Yahoo today will launch its own desktop search software, following similar launches by rivals Google, Ask Jeeves and Microsoft.

The company promised to launch Yahoo Desktop Search last month. Like competing products from Google, Ask Jeeves and Microsoft, the Yahoo software is being released as beta software.

Desktop search tools are designed to help users find information stored in their PC hard drives, a task that utilities included with the Windows operating systems traditionally have performed poorly.

Based on technology Yahoo licensed from desktop search specialist X1 Technologies, the Yahoo Desktop Search application can index over 200 different types of files, including those created by Word, Excel and PowerPoint and Adobe's PDF and PhotoShop. The tool can also index the content of Microsoft Outlook and Outlook Express e-mail messages and their attachments.

Yahoo Desktop Search lets users preview the content of the files it finds, so that they don't necessarily have to launch the files in their native applications in order to view them. The tool even plays audio and video files without the need to launch them in a separate media player. It also lets users sort, delete, print and share files it finds right from its interface.

Letting users perform a variety of actions on the list of desktop search results reflects Yahoo's "holistic view of search," said Bradley Horowitz, Yahoo's director of multimedia and desktop search. The search activity doesn't end with the delivery of a list of results but rather when the user has completed the task that prompted the search, he said. "This application delivers on that agenda," Horowitz said.

Another feature of Yahoo Desktop Search is that it searches for files as the user types the query, as opposed to waiting for the user to hit a search button. Yahoo Desktop Search also allows users to specify which files they want and don't want indexed, and to refine searches based on a variety of parameters.

Yahoo isn't trying to replicate the functionality of X1's desktop search product, Horowitz said. Yahoo's tool is being designed with consumers in mind, while X1's product is aimed at business users, he said. Moreover, Yahoo plans to tightly integrate its desktop search tool with its online services, such as its Web mail service and online address book. That integration will not be part of X1's product. A final and significant difference between the two products is that Yahoo has no plans to charge for Yahoo Desktop Search, while X1 charges for its application, he said.

Yahoo Desktop Search currently only works with computers running Microsoft's Internet Explorer browser on Windows XP and Windows 2000.

Other companies that provide applications for searching hard drives include Copernic Technologies, Blinkx, Lycos and - very soon, Apple.