Ccleaner - best tool to Clean your registry and temp files
http://www.piriform.com/ccleaner
This tool cleans temporary files from windows as well as most common programs. This is including your Internet browser which can amass a lot of junk
This tool will also clean your registry with any cobwebs from old programs you un-installed long ago. Speaking of that this program will also do a better job of un-installing programs then windows does.
Cost, Nothing
Open source to boot
