I have just built a new pc and installed windows 7.
Whenever I go into a game it crashes. There is no BSOD dump. I found this happens when it tries switching screen resolution while in fullscreen mode. If I run a game in safe mode or windowed mode they work fine. (After a crash I can't alt-tab or ctrl-alt-del etc but if I hit the sleep button and turn it back on I'll be back in windows)
The games that will run in fullscreen without crashing are GTA4, Crysis and Mass Effect 2.
Torchlight, Modern Warfare 2, Borderlands and others crash if they are not in windowed mode when executed.
I have an AMD Phenon 2 with nVidia GTX275. DirectX 11 in 1920x1200.
I have tried updating DirectX and my nVidia drivers but so far nothing works.