Google Desktop

http://desktop.google.com/

This free app from Google is probably one of the most convenient ways to search your computer’s files, folders, email and web history. After you download the application, it runs in the background, indexing your entire hard drive. Once that’s done, searching for something on your PC becomes as easy as using Google to search the web. Simply input key words or phrases, and every web page you’ve visited, email you’ve sent, or file you’ve created that’s relevant to your search will be presented as a list of clickable links. The program also features a ‘Sidebar’ – a widget that you can choose to display at the side of your screen containing a number of ‘Google Gadgets’, such as news headlines, weather reports, and RSS feeds.