If all you've tried is multiple copies of the same hardware models then I'd make a motherboard switc

If all you've tried is multiple copies of the same hardware models then I'd make a motherboard switch to a different model. If you've had this problem across different models then I'm not sure what's causing it. If the latter case then you might have some seemingly innocuous piece of hardware (modem, flash card reader, etc.) which is causing the problem but with the monitor turning off sometimes it's hard to blame anything other than the motherboard, video card, or PSU.So basically you had an older Athlon XP system running the original X700 and then decided to upgrade to an Athlon 64 and keep the AGP video card but also have a PCI-Express x16 for the future.You've had an X700 Pro fail with two completely different kinds of motherboards in the same way. And you've already tried two different X700s to make sure it wasn't a bad video card and tried multiple PSUs. I wish I had an answer for you but I don't. Given that you've been running various X700s, trying a completely different video card (presumably PCI-Express) would be the next thing I'd try. It's a little shifty but, around here, you can buy video cards from some retail outlets which allow returns with no restocking fee. I'd "try out" a PCI-Express card (I'd go with NVIDIA to make it as different as possible) to see what happens. Or, if you know someone with a PCI-Express machine, you could borrow their video card to see what happens. You've already replaced so many components that I'd try to get away from that X700.The only other things I can think to try before trying out another video card is to run the easy tests: RAM test, and a CPU test just to make sure you haven't missed any of the easy problems to diagnose. Then I'd remove every possible piece of hardware from your computer except those required to run a game and see if it still cracks up. If it still cracks up then you don't have much choice but go back to swapping in other hardware. Sorry.