WindowsXP is a big improvement over older versions, but it isn't exactly good at cleaning up after itself. For example, why doesn't WinXP clear its prefetch or temp folders from time to time? It's just one more little quirk to add to you list of maintenance duties. Yay.
Whenever you print something, WinXP automatically sends a temp file to your HDD. When the print job is finished, Windows is supposed to automatically delete this file, but guess what, sometimes the OS just leaves its junk laying around. If you don't like your HDD cluttered up with useless files, go to your system32\spool\printers directory and clear out everything inside. It's a manual tip, but one that will keep things cleaner in the long run.