"Cleanmgr" is a disk-cleanup manager included in all Windows from Win98 onward. It doesn’t do a lot in Win98, but has gained power in succeeding releases. In Win2K and XP, it’s actually a decent little tool that has the potential to clean quite a bit from your system, and can even automatically compress little-used files to make them occupy less disk space. Oddly, simply running Cleanmgr does NOT normally give you access to its full power: Instead, you need to modify it a bit.
We’ll get to the mods in a moment, but if you want more info on CleanMgr, click one of these links: