I installed this Desktop Google on my machine this morning and have been VERY impressed with this thus far.  It basically takes the same technology that Google for the web uses and applies it to the data on your hard drive.  It makes an index of all the contents of all the files and supports the MS Office line of products and well as AOL IM and others. 

Give it a shot and let us know what you think in this thread of the forums

Google Desktop Search
             Search your own computer.

  • Find your email, files, web history and chats instantly
  • View web pages you’ve seen, even when you’re not online
  • Search as easily as you do on Google

Google Desktop Search finds:

Outlook  Outlook / Outlook Express Word  Word
AOL IM  AOL Instant Messenger Excel  Excel
Internet Explorer  Internet Explorer Powerpoint  PowerPoint
Text  Text