Mountain View, Calif. ? Online search-engine leader Google is targeting the computer hard drive with software that promises to scour the clutter of documents, e-mails, instant messages and other stored files.

The free desktop-search program, unveiled Thursday at desktop.google.com, marks Google’s latest attempt to become even more indispensable to the millions of people who entrust the company to find virtually anything on the Web.

Google is betting the program will expand its search engine audience and encourage even more online searches than it already processes — a pattern that would yield advertising revenue, the company’s main moneymaker.

The program is a not-surprising step into a crucial realm.

Managing information glut is an increasing challenge for computer users, and the program gives Google a head start on Microsoft Corp., which is working on a similar tool but recently said it would not be ready for the next version of its Windows operating system promised for 2006.

Marissa Mayer, Google’s director of consumer Web products, called the program “the photographic memory of your computer.”

“If there’s anything you once saw on your computer screen, we think you should be able to find it again quickly,” she said.

That may give Mountain View, Calif.-based Google an advantage in luring traffic from its chief rivals, Microsoft’s MSN and Yahoo.

Computers displaying the Google desktop search engine are on display at the Digitallife show at New York's Jacob K. Javitz convention center. The free desktop-search program was unveiled Thursday at http://desktop. google.com.

Leery of raising privacy concerns that have shadowed its recently introduced e-mail service, Google is emphasizing that the desktop search program doesn’t provide a peephole into the hard drive, even when the product connects with the online search engine.