butterball is right. If that fan is not spinning power down the computer immediately and check all the connections on the video card for the fan. Spin the fan with your finger to see if it the bearings are still good. If you reassemble and the fan still doesnt spin get a fan kit such as the blue orb for your vid card.
And note the urgency in svtcobra voice. If you let it run for too much longer, you wont have a GF 3 for long. You will have a pretty paper weight though....get the blue orb or something similar....NOW....please