Just got word that TweakersAsylum have updated their Windows XP ACPI Tweak Guide. Below is their announcement:

A while back we did a guide on gaining 3D gaming performance by disabling Windows XP ACPI. This guide generated A LOT of interest and still does on a regular basis today! Due to the high demand, I decided to break down and do an update to our original guide. In this update you will find a new set of benchmarks, a few more tips, and even a couple of new tricks! Windows XP ACPI Tweak Guide - Updated