Use Crap Cleaner to remove temporary files and other junk you don't need!

CCleaner (Crap Cleaner) is a freeware system optimization tool that removes unused and temporary files from your system - allowing Windows to run faster, more efficiently and giving you more hard disk space. The best part is that it's fast! (normally taking less that a second to run) and Free. :)

You might also want to read this article that details a simple batch file to run ccleaner and exit automatically.