Can you be more specific as to what exactly happened? Assuming you got a Windows Blue Screen of Death? (BSOD)
This could be a software issue in Windows itself or an issue with the motherboard. You might want to update the BIOS on the system if not already done to see if that helps. If it’s software related, it could be that the NVIDIA drivers might be need to be completely uninstalled – there is a good tool for that here:
http://www.wagnardsoft.com/forums/viewtopic.php?f=5&t=749
If that doesn’t resolve it, and if possible, install Ubuntu and NVIDIA drivers on Ubuntu and see if the video cards work under Linux. If that works, you might need to reinstall Windows altogether.