extremetech has a great guide to help you speed up windoze!

Optimize Windows XP
A step-by-step guide to better performance.
By Joel Durham Jr.

Is XP the fastest version of Windows ever? That's debatable, but this is not: like every operating system that came before it, it's not as fast as it could be without a whole bunch of fine-tuning.

Windows operating systems are never streamlined by default. Part of the reason is that their install base is huge--many times that of any other operating system (in fact, probably every other operating system combined). No matter how well polished and optimized any Windows OS may be, Microsoft must balance performance with ease of use and across-the-board compatibility.

Therefore, Windows XP makes quite a few assumptions about how it's going to be used.

read the guide here