There are a number of things that cause Windows XP to slow down like fancy menus fading in and out. One thing I didnt realise was the highlighting of new programs in the start menu. TechBeyond have created a video of how to disable this from happening so that you can slightly cut down processor usage. Although you might not see a dramatic increase, it is still one thing that can be done easily.
Windows XP Tweak
Previous post: Toilet Paper Folder and Dispenser Prototype
Next post: BioVault