Have you ever sat down at your laptop and thought, "Oh no, my important file is on my desktop computer!" Or looked at your smartphone and said, "Sure would be nice if I could access my critical work files on the phone, but that's impossible!"
Of course you haven't. Because you're not an idiot. You most likely have installed a cloud storage and file synchronization service that does all that. If you're like most people, you picked the one with the most buzz: Dropbox. The service has 500 million users and 150,000 businesses using Dropbox Business).
Major companies like Google and Microsoft are in the same business, but always have their sync/storage offerings tied to other products (Google Docs and Microsoft Office, for example). In some ways, Dropbox's simplicity—it works with any of your files—makes it all the more attractive. More importantly, it just works—and even directly works with Google Docs and Microsoft Office! Of course it is not only a program for the desktop (Windows, Mac, and Linux) but is also accessible via the Web and on mobile devices running iOS, Android, Kindle FireOS, and Windows Phone.
Fine, Dropbox is a service lots of people like, but it isn't perfect. Many see it as overvalued; it's had some bad press, by adding people like Condoleezza Rice to its board and changing terms to force users into arbitration when there are legal disputes, and it killed a couple of beloved single-use mobile apps: Carousel for picture backup and Mailbox for getting your inbox to zero.
Maybe worst of all for consumers: Dropbox is absolutely stingy with doling out space for free to customers: it offers only 2GB of online storage for free, compared to Google Drive's 15GB (shared with Gmail and Google+), Microsoft OneDrive's 15GB, and Box (Personal)'s 10GB. Dropbox gets away with it by pushing users to pimp the service to get more space (as you'll see in the slideshow). An upgrade to Dropbox Pro costs $9.99/month or $99/year (both plus tax) and upgrades your space to 1TB (1,000 gigabytes).
So why use it? Like I said, Dropbox just works. Plus it does a lot more than just syncing. It's the perfect digital suitcase. It ensures you'll never be without your files wherever you need them, assuming you utilize Dropbox to the fullest. Just how do you do that? These tips spell it out.
Maximize Free Online Space
Dropbox appears stingy at first with its measly 2GB online storage allotment. But there are some quick ways to increase that space. First, complete the "simple tasks" (as Dropbox calls them) that earn an extra 125MB each. They include: linking Dropbox to Twitter, linking to Facebook, following @dropbox on Twitter, posting a comment about Dropbox to Twitter, and another to Facebook—that's 625MB right there.
The way Dropbox really wants you to earn space is finding it customers. For each person you send a referral that gets Dropbox a new sign up, you get 500MB (or 1GB if you pay for Dropbox Pro). If the person you refer already has an account, you get zilch. The max is 32 friends earning you a total of 16GB (32 for Pro). You could send yourself a bunch of referrals of course, but each one needs to create an account for you to get the space—it's not worth it. One enterprising person nabbed his max referral bonus space by placing a Google AdWords ads with the custom link, then ceasing the campaign once he hit the 16GB limit. Easy.
Also, keep an eye out for the company's occasional contest or coupons to score big storage, as much as 50GB extra. Or, pay the $99 a year (plus tax) to go Pro and get 1TB of storage on top of your earned space. That's the equivalent of $1.90 per week.
The way Dropbox really wants you to earn space is finding it customers. For each person you send a referral that gets Dropbox a new sign up, you get 500MB (or 1GB if you pay for Dropbox Pro). If the person you refer already has an account, you get zilch. The max is 32 friends earning you a total of 16GB (32 for Pro). You could send yourself a bunch of referrals of course, but each one needs to create an account for you to get the space—it's not worth it. One enterprising person nabbed his max referral bonus space by placing a Google AdWords ads with the custom link, then ceasing the campaign once he hit the 16GB limit. Easy.
Also, keep an eye out for the company's occasional contest or coupons to score big storage, as much as 50GB extra. Or, pay the $99 a year (plus tax) to go Pro and get 1TB of storage on top of your earned space. That's the equivalent of $1.90 per week.
Set Up Desktops via Mobile
If you have a new computer to add to your Dropbox account for syncing, you typically download the right software for your operating system, log in with your username/password (and maybe your extra token for two-step verification, see the next slide), and let it happen. The latest iOS and Android apps for Dropbox added a new feature: Link a Computer. Go into the Settings on the mobile apps, click it, you'll be asked to go to the desktop and visit www.dropbox.com/connect, and scan the QR code that hides within the Dropbox logo on that page. If you THEN install the Dropbox app, you'll find it fully set to go, no need to log in.
Secure Your Drop
Two-factor authentication is necessary when a password isn't enough. If you try to access an account from a new device, you'll need to provide a code or PIN that is sent to a device on your physical being (typically your phone). It's not foolproof, but it's stronger than just a username/password combo. Dropbox supports it. On Dropbox.com, click your name in the upper right to get the dropdown menu, select Settings, then go into Security. Dropbox calls it "two-step verification;" click Enable. From here, choose to get codes sent to you via standard SMS text, so it works with any mobile phone, or use a mobile authenticator app (I recommend Authy, free on iOS and Android and the Chrome browser). You'll use the app to scan a QR code; in the future, when you do a new login to Dropbox, visit the authenticator app to get that extra security code, called a token, to type in.
You can also secure Dropbox on your mobile phone--the app has the option to add another 4-digit passcode before anyone can access it. You'll find it under Settings > Passcode Lock.
You can also secure Dropbox on your mobile phone--the app has the option to add another 4-digit passcode before anyone can access it. You'll find it under Settings > Passcode Lock.
Access via Web for Old File Versions
People tend to think of Dropbox just for sync, but its access to files via the Web is great, providing full visual previews of documents when you click on them. The Web interface is also where it's easiest to set up shares, upload files (which you can do via drag and drop right on the browser, even to individual folders), and best of all, access past versions of files. Right click a file and select Previous versions—you'll get a full version history. If you make a mistake and save the file, you can revert back to a previous version as needed.
Make Dropbox Your My Documents
Windows users know that the Documents folder looms large as the place designated by the operating system for default storage (along with Music, Pictures, and Video). One of Dropbox's drawbacks (some would call it a strength) is that it will only works with one folder—the Dropbox folder. Everything that goes into that folder gets synced with your other computers and stored online. If you want to skip the hassle of selecting the Dropbox folder every time you're faced with a Save As dialog box, then designate Dropbox as your Documents default.
Your choices with Windows: Move the Windows default folders into Dropbox by going to Windows Explorer, looking under This PC, finding Documents (or any of the Library folders) and right clicking to bring up Properties. In the Location tab, put in the path to Dropbox (likely C:\Users\Username\Dropbox\Documents).
Another option: Change the default save location in programs like Microsoft Word, so it points to the Dropbox folder.Or, download the third-party app Dropbox Folder Sync—it will sync any folder you designate (but doesn't work with network drives).
Your choices with Windows: Move the Windows default folders into Dropbox by going to Windows Explorer, looking under This PC, finding Documents (or any of the Library folders) and right clicking to bring up Properties. In the Location tab, put in the path to Dropbox (likely C:\Users\Username\Dropbox\Documents).
Another option: Change the default save location in programs like Microsoft Word, so it points to the Dropbox folder.Or, download the third-party app Dropbox Folder Sync—it will sync any folder you designate (but doesn't work with network drives).
Extend Dropbox in the Browser
If you're living a browser-based life, there are other ways to get entrée to Dropbox quickly. Top of the list: a Chrome extension called EasyDrop, which puts a drop-down menu a click away that provides fast access to files. If you download a lot of stuff, skip moving it to the hard drive first with Download to Dropbox. It moves files from online directly to your Dropbox storage (which will, of course, sync it to your hard drive). Unless...
Selectively Sync Files
You're not required to have every single folder you store in Dropbox on every computer. For example, you may not want all your pictures and music to come to your work PC. Go into your desktop Dropbox app's preferences and click the Account tab. Tell Dropbox to NOT download those folders to your local drive by unchecking the box. They'll still be online however, and available via the Web or mobile apps.
Recover Files from Trash
Sometimes you delete a file by accident. In Windows or Mac, you'd just go to the Recycle Bin or Trash... unless you've already deleted its contents, too. Oops. Time to break out the unerase utilities, right? Not if the file was in your Dropbox folder. Instead, surf to your Dropbox account and click the Trash icon at the top that says Show Deleted Files. All the greyed out files and folders are those you deleted. Click it, and you get the revision history, so you can restore it to the Dropbox.
Secure Your Drop Again
It's no secret that Big Brother is watching, and companies like Dropbox are targets. (Snowden even said so—he recommends SpiderOak, a sync service that costs $12/month for 1TB of online storage.) What do you do when the feds are knocking and Dropbox might hand over your documents? Encrypt. There are services that specifically make it their job to do that for your files before they're shared on a sync service (be it Dropbox, OneDrive, Google Drive, etc.). BoxCryptor is one; Viivo is another. They work across multiple platforms, though BoxCryptor appears to have the advantage of working on more of them. Both are free for limited personal use.
Destroy Your Shared Dropbox Files
You like the option of having things you send self-destruct, Mission:Impossible style? The app Digify will do that. It integrates directly with Dropbox via apps for iOS and Android, or via the Web interface. Give a timeframe for the file to go buh-bye. Digify will also show you who viewed the file. It's not Dropbox specific, but the integration means you can send a file stored in Dropbox or Box or Google Drive via Digify, complete with destructo-deadline.
Sync Files Over LAN, not Internet
If you have more than one computer in your home and they all use Dropbox sync, turn this on right now at each PC. Open your Dropbox desktop app preferences and go to the Bandwidth tab. Click Enable LAN sync. It's that simple. Now, Dropbox will sync with Dropbox accounts on the local home network, rather than sending files out to the Internet and back (it'll still sync to the Web, of course.)
Sync Your Desktop App Data
There are certain programs you may want to use on multiple computers that are heavily reliant on local system information. It would be nice if those apps would do their own sync, but they don't. I'm talking about software like iTunes, Scrivener, iPassword, etc. Guess what? You can put their data folders/libraries in your Dropbox. Make sure the apps on each PC point to the right spot, and then all the programs should remain in sync as you move from desktop to laptop and on. (iTunes can be finicky about it; check out step No. 3 here for details to keep it in line.)
Create a Drop Zone
Imagine you're at a workplace where IT keeps PCs locked down, so you can't install the Dropbox app. What do you do when you have data that absolutely should be saved in your account? You could drag files to the website interface, but there are other options that create a "drop zone" where files will auto-upload. This is especially useful if you have other people you want to give upload access, but not full access, to the account, be they co-workers or clients or students. DROPitTOme will create a unique URL for people to use for direct uploads; JotForm creates embeddable online forms for uploading files; Send to Dropbox creates an email address that places all attachments in the associated Dropbox. Most drop zones will expire after a while.
Disconnect Apps and Devices
If you're worried that some stray app is using your Dropbox a little too much, you can disconnect it by visiting the list of Apps Linked on the Security settings. There's a full list of every app you've given the right to talk to Dropbox, be it in full or just in one folder. Click the X on the far right to disconnect it. Scroll up to view all the devices likewise connected, and feel free to dump those that don't belong. Hover over the little "i" in a circle icon (for "information") and you'll get some info, specifically OS version and IP address for each device.
Link to Mail to Avoid Attachments
Gmail gets a lot of mileage out of letting you link files in Google Drive to messages, and OneDrive does it with Outlook mail; both avoid the overhead of message size limits (typically 25MB per message). Well, Dropbox has that, too—with Yahoo Mail, Gmail, and Outlook. To make it work, link the accounts.
In Yahoo Mail, click Compose to create a new message, then click the attachments icon (the paper clip with a down arrow). Pick "Share from Dropbox" and you'll be asked to link. You'll also get a Save to Dropbox option when attachments arrive in new messages.
For Gmail, you have to be using the Google Chrome browser on the desktop; install the Dropbox for Gmail add-on. Then you can send and preview files from your Dropbox in Gmail messages, without leaving the Gmail interface.
Microsoft recently announced that Outlook.com users will soon have more options to work with Dropbox (and Box) files directly.
In Yahoo Mail, click Compose to create a new message, then click the attachments icon (the paper clip with a down arrow). Pick "Share from Dropbox" and you'll be asked to link. You'll also get a Save to Dropbox option when attachments arrive in new messages.
For Gmail, you have to be using the Google Chrome browser on the desktop; install the Dropbox for Gmail add-on. Then you can send and preview files from your Dropbox in Gmail messages, without leaving the Gmail interface.
Microsoft recently announced that Outlook.com users will soon have more options to work with Dropbox (and Box) files directly.
Upload Direct to Facebook Groups
There's one area of Facebook where Dropbox is integrated. If you are part of a Facebook Group, you can send a file directly to the group from your Dropbox for all the members to see. Click Add File at the top, link Facebook to your Dropbox, and you can pick any file to instantly share. Sadly, and strangely, this only works for Groups. You can't do it on a Facebook Page or your personal timeline.
Store Your Voice
Voice apps aplenty are available on mobile devices. Many just store the audio files on the handset, taking up precious space. If you want a little more permanent storage option that's accessible from the desktop, get a recorder that supports Dropbox storage. The perfectly named Dropvox ($1.99, iOS only) is the most obvious choice—every MP3 created goes right to Dropbox. Plenty of other apps will back up voice recordings to Dropbox, including Recordium Pro ($4.99, iOS), Smart Voice Recorder (free, Android), and Skyro Voice Recorder (free, Android).
Automate Dropbox
You knew there had to be an entry about integrating Dropbox with IFTTT, right? If This Then That is changing how we work with Web apps all the time, and its Dropbox channel means you can save items from many other services (Instagram, Facebook, voice recordings, iPhone photos, email attachments, etc.) with zero work. It also sends items saved in your Dropbox public folder (the only one IFTTT can monitor) to other services.
But IFTTT isn't the only game for automating Dropbox actions. Wappwolf's Automator for Dropbox arguably does a lot more. Give it access to one folder or your entire Dropbox contents. You link the accounts and start creating actions to take place when you add a file. It'll look at documents and convert them to PDF or TXT, and send them to Google Drive or your Kindle; with pictures it uploads to Facebook, Flickr, Picasa/Google+ or converts them or adds effects; it converts audio; it uploads video to Facebook, YouTube or Flickr; it can send files to a zip, to a service like Evernote or Basecamp and others; or just send info such as a tweet or Facebook status update. The downside: most of these actions are limited to premium accounts that cost $5 a week.
Likewise, the more business-oriented Zapier also has zaps galore that work with Dropbox, for copying items in services like Gmail or Evernote directly to Dropbox, or getting alerts when things happen within Dropbox. You can use 5 zaps for free, more than that you need to pay for the $20/month basic service on up.
But IFTTT isn't the only game for automating Dropbox actions. Wappwolf's Automator for Dropbox arguably does a lot more. Give it access to one folder or your entire Dropbox contents. You link the accounts and start creating actions to take place when you add a file. It'll look at documents and convert them to PDF or TXT, and send them to Google Drive or your Kindle; with pictures it uploads to Facebook, Flickr, Picasa/Google+ or converts them or adds effects; it converts audio; it uploads video to Facebook, YouTube or Flickr; it can send files to a zip, to a service like Evernote or Basecamp and others; or just send info such as a tweet or Facebook status update. The downside: most of these actions are limited to premium accounts that cost $5 a week.
Likewise, the more business-oriented Zapier also has zaps galore that work with Dropbox, for copying items in services like Gmail or Evernote directly to Dropbox, or getting alerts when things happen within Dropbox. You can use 5 zaps for free, more than that you need to pay for the $20/month basic service on up.
Host a Website or Wiki From Dropbox
Got a super-simple website you'd like to host? If you know the HTML and CSS and even Javascript (sorry, no PHP scripts allowed), you can put the files within a folder in your Dropbox public folder and people will see it as a website. Right click a file in the folder to create a Public Link you can share with the world. If you'd like to make a limited wiki that others can collaborate on, put a TiddlyWiki "non-linear personal Web notebook" file in the folder.
If that's too complicated, look at Dropages.com. It creates shared folders on your Dropbox account, you pick a domain name (my-site.droppages.com, for example), download a theme, and you drop in the content. Site44 promises hassle-free static sites edited in Dropbox, but hosted on Amazon's high-end cloud offering; it costs $4.95/month for up to 10 sites. KISSr sets up the hosting right through Dropbox itself for around the same price. Pancake creates a text-based website; it can still support images, spreadsheets, PDFs, PPTs, and even markdown files.
If that's too complicated, look at Dropages.com. It creates shared folders on your Dropbox account, you pick a domain name (my-site.droppages.com, for example), download a theme, and you drop in the content. Site44 promises hassle-free static sites edited in Dropbox, but hosted on Amazon's high-end cloud offering; it costs $4.95/month for up to 10 sites. KISSr sets up the hosting right through Dropbox itself for around the same price. Pancake creates a text-based website; it can still support images, spreadsheets, PDFs, PPTs, and even markdown files.
Mobile Favorites Are Local
Dropbox tips tend to be very desktop-centric because that’s where you interact with the actual files and folders the most. Mobile does let you move things around and delete them, but you can't do that, or even read a file, if your mobile device is not online. That changes, however, if you favorite a file. Open one in the mobile app, click the Star icon, and the file is now not only a favorite, but will be locally available on your tablet or phone, even in airplane mode. Very handy for reading stored ebook files or PDFs when you're still on the runway.
Ditch the Carousel for Photo Uploads
For a while, Dropbox offered a separate mobile app called Carousel to upload images take on your iOS or Android smartphones. It was a mostly set-it-and-forget-it option (which also, nicely, added 3GB of space to your Dropbox allotment). It made it easy to share pics and video instantly, too. But now, Carousel is dead (or will be as of March 31, 2016). Don't worry about the photos you've already uploaded using the app—they're still available at photos.dropbox.com/app/timeline or via the photos tab in the mobile apps. However, you may want to migrate any shared albums you have through Carousel direct to Dropbox, or you might risk losing access—the Carousel app can walk you through this; click yellow warning link in the app for the steps, but do it before March 31.
How do you replace the auto-backup aspect of Carousel to send your new photos/videos to Dropbox. Do it in the Dropbox mobile apps for iOS and Android. To make it work, you need to uninstall Carousel, then go into Dropbox on the smartphone, select Settings, then activate Camera Uploads.
How do you replace the auto-backup aspect of Carousel to send your new photos/videos to Dropbox. Do it in the Dropbox mobile apps for iOS and Android. To make it work, you need to uninstall Carousel, then go into Dropbox on the smartphone, select Settings, then activate Camera Uploads.
Don't Violate HIPAA
Guess what, medical pros? Dropbox is now HIPAA (Health Insurance Portability and Accountability Act) and HITECH (Health Information Technology for Economic and Clinical Health Act) certified, so you can use it to store patient records. Dropbox will sign a Business Associate Agreement (BAA) with you if needed.
If that's not enough, check out Sookasa. Put the patient info in a Sookasa folder inside Dropbox and it's automatically encrypted and tracked for you. Sookasa is also great for educators abiding by the Family Educational Rights and Privacy Act.
Write and Store Your Notes
Dropbox is all about storage, but while it's just like any folder on the desktop for file access, it's not really great at direct interaction with apps on mobile all the time. So if you want to keep notes on Dropbox, it's best to get a notepad app that specifically supports storage on the service. A few excellent options: Genius (Free, iOS), Write in the Cloud (free, Android), Droptext ($.99, iOS), Caret ($.99, iOS), and the utterly excellent Notability for handwritten notes (pictured above, $5.99, iOS). Here's a list of just about every iOS text editor ever made, showing which work with Dropbox.
If you want a desktop Web-based editor, try Draft, which can import documents already in Dropbox. Writebox has an option for the Web, a Chrome app, and iOS app to keep everything in sync.
If you want a desktop Web-based editor, try Draft, which can import documents already in Dropbox. Writebox has an option for the Web, a Chrome app, and iOS app to keep everything in sync.
Android Perks
If you're using Dropbox on Android, here are a few cool tricks:
First, download Easy Backup and use it. It's a full backup app for your Android data (apps, texts, calendar, etc.) that utilizes your Dropbox space. It's free.
If you use app stores other than Google Play (such as Amazon's Appstore), you'll get APK installation files. Find them and store them in Dropbox. Then you can uninstall the apps and reinstall as needed.
The official Dropbox app for Android doesn't put your files on your device, it provides access to them over the Internet (you can favorite a file to make it local, remember?). Get guaranteed two-way sync from the free Dropsync app, which treats your Android like it's a desktop, filling it with your Dropboxed files. Don't set it up if you have more files on Dropbox than you do capacity on your Android device. Instead, try Folder Downloader for Dropbox to keep only one folder in sync.
First, download Easy Backup and use it. It's a full backup app for your Android data (apps, texts, calendar, etc.) that utilizes your Dropbox space. It's free.
If you use app stores other than Google Play (such as Amazon's Appstore), you'll get APK installation files. Find them and store them in Dropbox. Then you can uninstall the apps and reinstall as needed.
The official Dropbox app for Android doesn't put your files on your device, it provides access to them over the Internet (you can favorite a file to make it local, remember?). Get guaranteed two-way sync from the free Dropsync app, which treats your Android like it's a desktop, filling it with your Dropboxed files. Don't set it up if you have more files on Dropbox than you do capacity on your Android device. Instead, try Folder Downloader for Dropbox to keep only one folder in sync.
Dropbox Finds Stolen Devices
No one would claim that Dropbox is as good as Find My iPhone, but if you "lose" a laptop, there's a chance Dropbox can help. Dropbox automatically starts and logs in on most PCs, so it should do that when a thief boots it up for the first time. Go to the Web, log in and get into your Dropbox Settings, and click Security. Scroll down and you'll see Sessions—it will show you the most recent logins to your account. If one matches your missing notebook, hover the cursor over the "i" for info icon—you'll get a time of the last use and an IP address, which you can take to the cops.
Listen to Media
Your Dropbox storage is meant to be just that, storage, not a drive you can stream or play from. But it's easy enough to do that with the right apps. For example, Bound for iOS ($2.99) lets you play DRM-free audiobooks you've stored on Dropbox (though it's not really streaming them). The same goes for the MP3 Music files you've got stored, if you want to use the free Jukebox for iOS. Again, not streaming, but it's an easy cheat to listen quick without throwing files into iTunes to sync with your iPhone. The service JustCast turns any audio you store on Dropbox into an RSS-fed podcast you (or anyone you share the feed with) can access in a podcasting app. It even publishes the files to iTunes.
On the Android side, the venerable DoubleTwist app called CloudPlayer could do the trick for both, as it looks at music/audio files on Dropbox, Google Drive, and OneDrive then lets you stream or download them to play.
On the Android side, the venerable DoubleTwist app called CloudPlayer could do the trick for both, as it looks at music/audio files on Dropbox, Google Drive, and OneDrive then lets you stream or download them to play.
Request a File from...Anyone, Anywhere
It's easy enough to create a drop-spot for multiple people to upload files to your Dropbox—services like Balloon.io take care of that, creating a URL on which anyone can drop a file. But sometimes, you just one important file from one person—and if that person (or group, actually) doesn't have Dropbox, you don't need anything more fancy than to send them a request. To make a simple request, go to your account on the Dropbox website, click File requests on the left, then Create a new file request (we told you it was simple). Create a folder for holding your requested files, then send off the request. The requestee will get an email with links to make sending the file to Dropbox a breeze. You'll get an email whenever new files are added based on the request; only you can see the requested, uploaded files.
Do Business as a Team
You can pay extra ($15/user/month) for the features of Dropbox Business, which includes things like unlimited space and file recovery; but if you're happy with the basic or even Pro ($9.99/month) versions, create a Team —for free. The organizer gets some control over what becomes a dedicated folder for the workgroup, like preventing others from seeing files they shouldn't. And don't limit a Dropbox Team to just work. This works for a family or friends who are collaborating on any kind of project. Any in the future, any Team member can upgrade the team... to Dropbox Business.
Put PC Files on Dropbox From Anywhere
Spotdox is an interesting product/service for a kind of one-off problem. If you forgot to put a file from your PC on Dropbox, sign in with Spotdox (when it's pre-installed on the PC running Windows or MacOS) and you can send the files to the service, from your smartphone or browser. It's like TeamViewer remote control, but using Dropbox for the remote access. Spotdox has free apps for iOS and Android. It will cost you $4/month or $24/year or $79 for a lifetime subscription to use after the demo.
Make Permanent Deletions
It's great that Dropbox has versions of your files going back 30 days (or a year if you're using Pro/Business). But sometimes you want to delete a file and make sure it's gone for good. You can: go into Dropbox via the Web, click the Trash—that's the icon next to the search box. (Don't go into Deleted Files—that's only for restoring files you want back). Now you'll see grayed-out deleted files listed alongside all those you still want; hold down the Ctrl key to select the grayed-out file (or files or entire folders). At the top, you'll see two options: Restore or Permanently Delete. Choose wisely.
Dropbox still has the files in your cache on your PCs however for up to three days! If you can't wait the 72 hours, you need to set your system to show hidden files, then go into the Dropbox folder (in Windows type in %HOMEPATH%\Dropbox\.dropbox.cache) to delete them.
Dropbox still has the files in your cache on your PCs however for up to three days! If you can't wait the 72 hours, you need to set your system to show hidden files, then go into the Dropbox folder (in Windows type in %HOMEPATH%\Dropbox\.dropbox.cache) to delete them.