help with an 8800gtx

Hey folks

My brother has a dell xps 720? it has a q6600 no overclocking, 3gb(3x1gb) of ram, 8800GTX, soundblaster x-fi(cant remember which one specifically),dells version of the 650i mobo,and windows vista home premium 32bit. he plays a lot of LOTR. lately his graphics driver will crash while he's playing LOTR. i told him to check his temps and to get atitool to see if he has artifacts. atitool said that he had an unrecognizable graphics card and that it could not show the 3d window.
gpuz showed that he was idling at about 54deg C. he does not have any problems with this driver in any other games he plays(witcher crysis bioshock). what happens is he will be playing and randomly the screen goes blank. he can still talk and hear the other people online. he then has to hit ctrl=alt=del start the task manager end the game and restart the computer.

any suggestions?

ps, i dont know which driver he is using but i will try to find out when i get home tonight.