Nvidia FX5600 card problem
I have this FX5600 video card made from Sapphire and I had the same problems as many people here posting that the card was locking up or giving them other problems playing games.
the symptoms are: all 3D games locking up at random times or giving me fatal error messages. this would have me beleive the card is either overheating, the fan stopped spinning, or something is wrong with the memory. none of which were true.
the solution for me was easy. i have all my computers ghosted so all i had to do is restore the image of my system. all the games run fine now. this makes me think it is some sort of software problem. i'm thinking it's either the drivers are corrupting or some other software/ driver is conflicting with the video card drivers.
so this is something for you guys to think about when another person asks about a FX5600 problem, or even any of the FX series cards. i would tell them to reinstall the video drivers or at a last resort the OS since if it is a system software conflict nothing else may work.