Cheers Warp2Search for this heads up on this excellent article.
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.
If you spend a few minutes eliminating applets and services you don't need, and are willing to sacrifice some of XP's visual goodies, you can noticeably improve game and application performance on an XP box. XP itself even helps by optimizing its file system based on your computing habits, and Microsoft provides a few hands-on applets to speed up the optimization process.
Many of the optimizations we present here will require registry editing or employing other system-altering modifications. You'll need administrative privileges on the machine in question.