Here's a set of links that I've taken to using as a guide every time I reinstall windows which should help you out. They were written by Darksamurai in the spring of '03, but are still relevant as hell today.
How to Tweak the EVER-LOVIN' CRAP out of Windows XP! (PART 1) How To Tweak The Crap Out Of Win XP: Part 2 Tweaking The Crap Out Of Xp: Part 3 How To Tweak The Crap Out Of Win Xp: Part 4 Tweaking the CRAP out of Windows XP Vol. 5!
Took me about 45 minutes of digging to find those, but there they are. Hope they help.
PS, Show Darksamurai some love for putting those posts together to help us pimp all the extra goodness that we can out of our Windoze xp systems!!