The problem started when I switched out my EVGA GTX280 and install my old EVGA 8800GT, and it's getting worse. Windows Vista x64 SP1, 190.xx WHQL driver and mobo bios F6h = random freeze when booted into Windows, if it doesn't freeze within 10 mins, it could run for days. And if I shutdown the computer for a night, it would happen again. Windows Vista x64 SP2, 191.xx WHQL and bios F9h . 9 out of 10 time, it couldn't boot into Windows with NVIDIA driver installed (freeze after the loading screen, black screen). It ran just fine if It passed the loading screen and happen again if I restart, shutdown the computer. Once I uninstall the driver using safe mode, it booted into Windows just fine. Rolled back to 190.xx = same thing. Only freezing, no bluescreen. Reset bios to fail-safe mode did not fix the problem. Any idea what's wrong?