Right the way i see it, there are two options.

1. http://www.musicxp.net. There are a whole list of optimisations for XP on here.

2. Turn up the latency on your sound card. For example turning it up from around 10ms to something like 20 - 25ms will make a huge difference.

Oh, I will add one more suggestion. You could do what i did, and get a 2.4ghz QUAD CORE with 2 GIG of Ram. OMG it flies!!!!!! I cant get it to stutter ;)