I highly recommend this utility.  It's 100% free and will help keep your system running FAST.
Cleans Temp Files, History, Cookies, and much more.  It also features a registry repair & cleaner.
I personally use this product and it WORKS VERY well.
WORKS WELL WITH VISTA AS WELL!

RECOMMENDED DOWNLOAD: CCleaner.

CCleaner is a freeware system optimization, privacy and cleaning 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. Additionally it contains a fully featured registry cleaner.
But the best part is that it's fast (normally taking less than a second to run) and contains NO Spyware or Adware! :)

KEY FEATURES:

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 Media Player, eMule, Kazaa, Google Toolbar, Netscape, MS Office,
Nero, Adobe Acrobat, WinRAR, WinAce, WinZip and many more...

100% Spyware FREE
This software does NOT contain any Spyware, Adware or Viruses.

There are several different kinds of programs out there to delete temp and junk files on your computer. 
Although PC Market Inc. does not endorse any particular product, this is an opinion of the store’s administrator James A. Pavicic, Jr.