Is there a program that can instantly search through my files to identify say, a certain name, phrase, etc?

For example, say I think I have a billing on file last year for ROBERT SMITH
But for whatever reason I cannot find it. Is there a program that will come up with any files with that certain name it it: In this case Robert Smith??

Any suggestions will be appreciate,

HeadRanger in San Francisco

Sure, here's a good one:
Google Desktop Download

After you install you will have to let it index your files of course.