This is a good site for hardware and software from ZD/PC Mag and on it are 19 Brand New Extreme Windows Tips
Optimize Windows XP
Windows XP Kernel Enhancements
Windows XP:Price, Performance, Pitfalls
and its index at Index which will give you an idea of the rest of the territory covered on this site. Another nice feature of this site, is that you can make your own library and store all the articles you want on the website to acess any time.