Check out
CCleaner. (Crap Cleaner, originally).
It has options to clear all the windows temporary files left behind by other programs such as Firefox, Internet Explorer, Media players, program installer files, as well as the Hotfix Uninstallers (under Advanced; Hotfix backup files can take up 100's of MBs). I'd recommend checking anything under Advanced except for "Wipe Free Space" and maybe Window Size/Location cache if prefer the window sizes you've created. I've saved over 1.5 GBs of temp/hotfix files from fresh XP installs on tons of computers.
Go to Options>Advanced and uncheck "Only delete files in Windows Temp folders older than 48 hours."
The program also offers a nice registry cleaner as well.