Random Crash, need advice

My new HP a1130n has been locking up. They only thing I have done to it, is add a new ATI X700Pro 256 PCI-E card. It runs fine normally, however, if left on prolonged or if I game for more than 4 hours or so, it locks up. Here is what I mean, when I exit the game (WoW), I can start to surf the net, but about 30 seconds into it, my screen freezes, then goes black, then comes back up with random color patterns and blotches, and the computer is hard locked, and requires a hard boot. I think it may be a possible cooling issue with the graphics cards. However, it is fine until I come out of the game, most of the time. Hopefully, you can make some sense of my post I can't post screenshots since the CPU is hardlocked, or I would

Thanks

It could be an overheat problem... Alt tab the game after a few hours of play and check the tempetures on the GPU (and CPU and stuff, you can get the temps on the GPU from the ati drivers I think, but you'll need to download a program to get cpu readings and stuff). Check temps while running all sorts of CPU tests (prime95).

If it's not the heat than it might be the ram... Run memtest86 overnight or something and see how it goes.

And last but not least, update drivers. Bios, chipset, graphics, sound, etc... With systems being so complex nowdays, even a sound card driver issue can cause lockups that look like graphic card overheats and stuff...

I left the side open last night, and put a small fan blowing directly into the case. After about 5 hours of gaming, it did the lock up thing. I turned it off (had to hold in the power button). I felt the heatsink on the graphics card and it felt warm.....if not cool. Anyhow, I ordered a new X800xl card with an awesome cooler, so I am going to return the x700 and see if that fixes it. I will keep you guys updated. Thanks