Well your sence of touch should be good for testing the graphic card temp. If you can't leave your hand/finger on it for a good amount of seconds, the card is too hot. Its better to touch the heat sink (the metal thing on the underside of the card) then any other area of the graphic card. Watch out for a fan if your card has one. Don't nick your fingers on it and make sure the fan is spinning. I just had to replaced my graphics card's fan yesterday. Check the temp right as the game crashes, it would be hottest at this time.
(Thinking about it, if the card was overheating, it would more likely freeze the computer then crash to the desktop, so this is most likely not the problem. It should be checked anyway.)
(I may not agree with thoughts posted under this name)
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