I have this issue with my dual display, when I drag any window from my main monitor to my second monitor it lags.
It worked fine with Vista and Windows 7, shouldn’t be any reason for it not working in XP.
I’ve install drivers for Chipset, Graphics and everything else.
Graphics card: nVidia 9500GS 512MB.
(also, I won’t be here for around 3 days. Please be patient for replies. )