Tweakhound's Eric Vaughan has updated his Windows XP tweaking guide to revision SP2 version 2.0 Final! this has to be one of the best tweaking guides around. This guide is all about optimizing XP. The purpose of this guide is to help you increase both the performance of Windows XP and and to customize the various settings to your personal preference. The goal is "Your computer, your way."...There are so many changes spread out over several months that to be honest, I have not kept track of them. Every page of this guide has been updated since the last final version.

TweakHound's Super XP Tweaking Guide - version 2.0 Final