After 15 years of messing around with every version of Windows available, I would say: going from Windows 7 to XP and then complaining about buffer/latency problems is a bit like exchanging your Porsche for a Corolla and then being miffed because of the lack of speed.
Have you tried DPC Latency Checker (
http://www.thesycon.de/deu/latency_check.shtml) to get a general overview of what's happening on your system?
El-Rallef