Optimize Windows XP to improve both work and gaming performance safely. Windows XP's default configuration is far from optimized. This guide will help you improve your overall system performance. I avoid using or recommending "all-in-one" Windows XP Tweak programs since many blindly adjust settings that have no affect on performance and can cause future problems.. This guide is designed to be performed top to bottom, in sequence since some steps are required to be performed before others. Before using this guide make sure your system meets Microsoft's Official: Windows XP System Requirements

This guide is not designed to be used in combination with other Windows tweaking guides or other Windows tweaking software. It is also not designed to be used in parts.

Optimize XP - A Windows XP Optimization Guide v1.7.7

Updates:
SP2 TCP Slowdown Fix
XP-AntiSpy Instructions