Windows 7 Tip: 
Cleanup Assistant is a simple free program for doing basic hard disk cleaning. This simple freebie helps speed up your system by unclogging your hard disk by finding duplicate files, cached files, and others, then deleting them for you. Cleanup Assistant features 7 tools designed to help you clean up your computer both manually and automatically:
* Large Folder Finder
* Empty Folder Finder
* Duplicate File Finder
* Drive Cleaner
* Privacy Protector (File shredder)
* Drive Wiper
* Remove Programs
It’s free, and easy to use, so even though it may not be the most sophisticated of programs, it’s is worth a shot.
Download Cleanup Assistant
Cool! Another tool that can do exactly the same thing is Glary Utilities. Looks pretty easy to use for me.