I have exactly the same problem with CRPG as mentioned here, since I was forced to chance my OS back from WIN7 to XP.
My System is an AMD 4600+ Dual Core with 2 GB DDR2 Mem and a Geforce GTS 450 with 1GB Mem ans is running Win XP SP2.
Drivers are all up to date. Although the System is not quite brand new, I achieve 135% Graphics Performance and the Native Modul is running smooth and without any Problems.
In June I played with Win7 on this PC with exact the same hardware (apart from a HDD, which got damaged and had to be replaced) and all was fine with CRPG. I will now upgrade to XP SP3 but have no big hopes that it will fix the CRPG-bugs. This seems to be a XP-specific problem for me. Changing back to WIN7 is the last option, though it has other drawbacks.
Any suggestions or solutions for our problem will be highly appreciated.
Sincerely
Steiner