http://www.theorica.net/gamexp.htm
Game XP is intended to optimize the performance of your computer for gaming needs. It tweaks and modifies various XP settings (cache settings, CPU priority etc.) and optionally disables or stops several Windows services that are usually not needed. The program does not require any installation, and does not need to be running at all times. Game XP extends your operating system's capabilities and makes Windows faster and comfortable for maximum gaming experience.