XP is ungodly slow on a highend system

Alright, now I'm no slouch when it comes to PC's but this has me stumped...

I recently purchased a relatively high end system:
Intel q6600 (G0 stepping)
Gigabyte P35-DS3R
4 GB Mushkin DDR2-PC6400 4-5-4-11-2t (4X1GB sticks)
Aundigy 2 ZS Platinum
XFX Alpha Dog 8800GTS
WD SataII 500GB
Seagate Barracuda 7200.7 160GB (The HD XP is on)
Nine hundred case

I'm running dual boot Vista, XP. And yes, I went the hard route of having Vista installed first. After some screwin around I got it all running.

Now Vista runs flawless on this system, however, I am a producer and run a large quantity of audio programs. Many of these are legacy Dsound programs.

Now my XP install runs like molasses on a cold day in the north pole. I'm curios if there are any switches etc I have to change in the ini files to get XP to play nice with my hardware, or the screwin' around with the MBR and boot.ini files has caused some sort of bottle neck in my system.

Anyways, I'd appreciate any help I could get. It's currently taking me close to 30 minutes to render out tracks. :\

Sorry forgot to mention in the original post.

XP has been running slow since install.