Here is a list of items you can do to *significantly* speed up XP, and by extension, your system.
For most users, proceeding to step 4 is all that is necessary, and you do not need RAM to burn to increase by a large margin the performance of your system.
For steps 5 and on, you will need to have a little bravery, a LOT of RAM, and really are only recommended for a power user.
Activating XP's Clear Type fonts will make your internet life 100% more crisp and clearer. Like Regular T.V. Vs HD.
If you do nothing else, do that.