Artifacts while gaming

[Nem2k]

the screenshot below should explain the problem

http://www.metallica.plus.com/artifacts.jpg

anytime I play a game, after about 5-10mins I get these artifacts all over the screen and it stays like that until the next day pretty much. no amount of restarting will get rid of them

and during some games, the screen would randomly go off every few minutes. and sometimes even randomly restart the computer

i updated to the latest drivers but doesnt seem to have gotten better

so im wondering what the problem could be?

a fried graphics card? overheating graphics card due to bad case cooling? a cpu running too hot?

before I make a decision about replacing either my graphics, cpu, or the case, I need to know which is the most likely problem...

 

[Nem2k]

erm ive only had the card and this computer for a year. well, not even a year old, had it since Jan 07

can graphics cards seriously die in that time??

but what im left wondering is how this happened? whats the cause of it?
because if I RMA or get another one, then I dont want it to happen again to my new graphics card if its something im doing....

 

[Nem2k]

hmm i couldnt find the option for vertex shaders but this problem isnt specific to wow, happens in half life, and UT3 demo as well. well, in UT3 the game just locks up and screen goes blank every 2minutes or so, completely unplayable

but are you sure that its the graphics card? could it possibly be the cpu? or the motherboard that i pushed too hard?
cos I dont want to buy a new graphics card just to find out I had actually burnt out the motherboard chipset or something