i have installed a fresh xp pro on a 2nd partition and applied all balckviper tips (www.blackviper.com).
Also, all the drivers can easily be found on the preinstalled 1st partition.
I have a RME multiface and this system is PERFECTLY stable and REALLY fast. I also own a dual G4 mac, and although it's more stable and feels "lighter" than the preinstalled vaio XP pro install (with all applications sucking cpu time, stability and memory), it doesn't feel as tight and stable as the LIGHT xp installation.
bottom line : once tuned and streamlined, my vaio with xp pro is the best computer i ever used for music.
but i'm quite paranoid about it : i am very reluctant in installing new software on it and would never install office or such craps.... (i have the 1st partition for that).
also it is very good looking