Following recent entries by Google and Microsoft among others, Yahoo! jumps into the steaming-hot desktop search race. The company is partnering with search leader X1 to offer Yahoo! Desktop Search (YDS), an impressive, free product for users of Windows XP or 2000, which earns our Editors' Choice award for free desktop search engines. YDS has almost all the features of X1 Search version 5, which will be released by the end of January, along with a Search Web button that links directly to Yahoo! search online. The main X1 features not present in YDS are support for Eudora and Mozilla e-mail clients, the ability to index offline PST files in Outlook, and support for indexing remote drives across a network. While YDS and X1 are very similar at present, future versions are expected to diverge.

YDS starts by indexing your local files and Outlook or Outlook Express e-mail messages, and allows very fine control over precisely what gets indexed. On a folder-by-folder basis, you can choose to index nothing; just file names and sizes; file names, sizes, and content; or everything. You can add to the default list of file extensions whose content is indexed, if desired. For e-mail, you can choose which folders to index, including Deleted Items and archived PST folders that are displayed within Outlook.

YDS indexes files and e-mail messages on a user-defined schedule, and can be configured to delay an indexing pass if the PC is busy. This delay option may be useful on slower systems, as YDS can use 90 percent or more of CPU resources while indexing. Recently created or changed files and recently sent or received e-mail messages won't show up in YDS until the next indexing pass. But the status bar always shows the indexing status; for example, "Last indexed today at 8:52 AM." Clicking on the status information brings up a display including an option to update the index immediately, thereby incorporating the most recent items. Unlike Ask Jeeves Desktop Search, blinkx, Google Desktop, and MSN Deskbar, YDS gives you full control over the location for the index files, so you can, for example, put them on a partition with more free space.

Searching with YDS is simple. You can either launch it from its system tray icon or search directly from the toolbar it installs in Outlook. To start, you click on a button selecting the search domain: E-mail, Attachments, Contacts, Files, Pictures, Music, or All. Initially it displays every item in the category, but as soon as you start typing, the list narrows down to items indexed on a word that begins with what you've typed (which also means that you can search on prefixes, but no other substrings). Results are displayed in a columnar view, which you can fine-tune by entering field-specific search terms at the top of any column. This instant search-as-you-type will suffice for most searches, but if necessary you can search on phrases, Boolean expressions, or whole words rather than prefixes. If you perform a particular complex search repeatedly, you can save it for re-use.

When you select a found item, YDS displays a detailed preview in its right-hand pane, highlighting all instances of the search term. A huge number of file types can be previewed including e-mail messages and most common word-processor, spreadsheet, database, and presentation formats. Graphics are displayed at full size rather than as thumbnails; audio and video files appear in a media player. In addition, the preview area includes buttons for common actions such as opening a file or its folder and replying to or forwarding an e-mail message. We did find the preview rather slow when previewing a huge text file with many instances of our search term.

YDS is particularly handy for those who tend to archive older files using ZIP or another compression method. It indexes files stored within a variety of archive formats including GZ, LZH, TAR, and the ubiquitous ZIP, and will also preview files within these. By contrast, Google Desktop will index archived file contents but not their names, and MSN Desktop requires purchase of a third-party iFilter module before it can handle ZIP files.

The product does have a few limitations. Unlike MSN Deskbar and Lookout for Outlook, it does not index Outlook appointments, tasks, or notes (X1 shares this limitation). Where Ask Jeeves and blinkx let you control the indexer's speed versus its CPU usage, YDS only allows you to postpone indexing if processor cycles are needed elsewhere. And it won't sort results by relevance the way MSN, Lookout, Google, and blinkx do.

X1 Search is a PC Magazine favorite; we even named it one of the best products of 2004. Yahoo! Desktop Search gives you almost all the power of X1, and it's free (X1 4.0 is $74.95). If you absolutely need the ability to search every type of Outlook data or index remote drives, it won't do the job. And it doesn't support Windows 98 or Me. But for most users it's an excellent choice.

You can download the Yahoo! Desktop Search beat at http://desktop.yahoo.com.