CCleaner is a system optimization and privacy tool. It removes unused files from your system - allowing Windows to run faster and freeing up valuable hard disk space. It also cleans traces of your online activities such as your Internet history. But the best part is that it's fast (normally taking less than a second to run) and contains NO Spyware or Adware!

Cleans the following:
Internet Explorer ; Temporary files, URL history, cookies, Autocomplete form history, index.dat.
Firefox ; Temporary files, URL history, cookies, download history.
Opera Temporary files, URL history, cookies.
Windows ; Recycle Bin, Recent Documents, Temporary files and Log files.
Registry cleaner ; Advanced features to remove unused and old entries, including File Extensions, ActiveX Controls, ClassIDs, ProgIDs, Uninstallers, Shared DLLs, Fonts, Help Files, Application Paths, Icons, Invalid Shortcuts and more... also comes with a comprehensive backup feature.
Third-party applications ; Removes temp files and recent file lists (MRUs) from many apps including Opera, Media Player, eMule, Kazaa, Google Toolbar, Netscape, MS Office, Nero, Adobe Acrobat, WinRAR, WinAce, WinZip and many more...