Help diagnosing computer video problem

My computer appears to be sick with what I’m assuming is a hardware problem. I don’t have any spare components sitting around to switch stuff out and determine where the defect lies that way, so I’m hoping if I describe the problem some helpful dopers will suggest what the offending part might be or some tests I can do to narrow down the suspects. I suspect that its the vid card, but I’m hoping someone will come along and suggest something else (read, something cheaper to replace).

So problem: when playing any sort of semi-graphically intensive games I start getting various image defects: odd polygons in the way, discoloration, lines across the screen, etc. It usually gets bad enough within a minute or two of when I first notice it to make the game more or less unplayable. When I quit out of the game, the computer starts to go back to windows, appears to freeze up and then the screen stops getting a signal and I’m forced to restart. This problem sometimes appears within the first minute or two of starting a game, sometimes 15-20 minutes in.

Stuff I tried: updated drivers (didn’t help), checked CPU temps (fine), checked GPU/CPU fans (fanning along merrily), tried a few games to make sure its not specific to just one (same problem with all).

Computer: AMD 3000 chip, 1GB RAM, ATI x800 vid card, err…not sure what the motherboard make is but I can check if it’ll help.

Reseating the card is something to try, but I’d have to say it doesn’t seem terribly likely, given your symptoms. Reseat the RAM while you’re at it.

Heh, I forgot the first rule of fixing complex modern electronics: jiggle stuff around and see if that helps. I reseated the card and couldn’t get the problem to repeat itself, so that might have actually been it.

I’ll bump this if the problem reappears in the next few days, but hopefully that did it. Thanks for the advice.