The hard disk drive on your desktop computer functions as the digital equivalent of a file cabinet, complete with a similar problem: it's easy to misfile documents. Text-search software can help in a variety of ways. You can find misplaced files by searching for a word or phrase, and the software will display every file that contains the text on the hard disk. When you expect your search might turn up a lot of files, you can exclude some files by using qualifiers such as "and," "not," or "or" and retrieve only those files you want. Using such qualifiers is called Boolean searching.

Effective text-search software need not be expensive:

* GOfer (about $50) from Microlytics Inc., in Rochester, N.Y., for IBM PCs and Macintoshes scans every portion of the hard disk you specify. As a result, a search may take a minute or more with a large hard disk.

* Dragnet (about $100) from Access Softek, in Berkeley, Calif., is a search program that works under Microsoft Windows on IBM PCs and can find text within graphics files. If you are searching for a quarterly report, Dragnet will dig up not only letters and reports but also graphs.

* Magellan (about $120) from Lotus Development Corp., in Cambridge, Mass., is a multipurpose IBM PC program with text-searching capabilities. It indexes your hard disk, which makes searching fast, a few seconds at most.

* On Location (about $80) from ON Technology, in Cambridge, Mass., for the Macintosh also indexes for quick searching, but it cannot do Boolean or phrase searches.

-- Cary Lu