I find people charging for system optimisation and trouble-shooting information on the Internet (musicxp.net, experts-exchange) embarressing.
In reality the people charging for that stuff have simply garnered information from other people on the web and real life who have - in the majority of cases - given it away, for free.
With that in mind I put together a guide for optimising XP systems for optimal performance in 2005, based on my experiences and the experiences of others from many, many forums and other sites on the internet. Today I've significantly updated it, given it a domain and provided links to all relevant software.
A little bit of info about myself: I program, have a BSc in Computer Science and frequently build systems for people, so I have some idea of what I'm talking about. I also run a small music studio in New Zealand, Soul Studios.
I hope sincerely that this guide helps you and the people around you-
Bom Shankar,
Matt Bentley
The Guide - Windows XP cleanup/speedup for Beginners, Experts and DAW-users