I have the exact same setup, msi kt333, brand new turtle beach santa cruz, win xp, 512 mgs of ram, and a amd xp 2000+ if I remember right.
There were problems but I think updating windows drivers, turtle beach drivers, and more importantly using the msi bios and motherboard driver utility fixed them.
You may try to use the motherboard safe defaults during install, and make sure you tell your motherboard not to run the onboard sound in the bios. Great card otherwise.