Since two years I use the best desktop search tool I know: Copernic Desktop Search.

With this tool it’s incredible easy to find the article, picture, presentation, e-mail that you need, but can’t remember where you put it. It’s a free download program and it indexes everything on your computer everytime you are not working on it. Just give it a try: the interface is also very nice!

This is what Wikipedia says on it:
Copernic Desktop Search is a desktop search utililty for the Microsoft Windows family of operating systems. It is designed to allow the user to instantly find a wide variety of items including documents, pictures, music, videos, e-mails, contacts, browser bookmarks/favourites and entries in the Internet browser history on the computer, external drives and network shares.

In this video it’s presented by CNet: http://www.cnettv.com/9742-1_53-20554.html