We blew out the dust on the computer. There wasn't much and the fans were turning fine. We checked all the capacitors and they looked good, though they were solid ones and I'm not sure how to tell if they might be bad. Then we opened up the video card and saw that the heat sink paste had completely dried out and so we put on some new paste. The game ran for awhile and then shut the computer down again. Next we exchanged the power supply for another and when we tried the game, it ran for a long time, so I hope the problem is solved.