My system:
XP2500+ @ 2.2ghz (3200+ spec)
1gb ram
9800 pro cat 4.4's
nforce 2 board and using onboard sound
Fortunately I've never had lockups or kicks to windows, from the UBi boards Revvin you are not alone, seems most seem to blame it on video, but I'm not so sure thats the issue...
What you using for sound? If you are using onboard sound, try getting just the audio driver and not the unified nforce drivers.
SKurj