Sufficent video card heats up and causes game to crash. Help!

[pokeytrev]

First of all, some system specs

Windows 7 64-bit OS
4 GB ddr2
AMD Phenom II X4 B40 Processor (4 CPUS), 3.0 GHz
Nvidia GeForce GTX 470

In the past I played the game, didn't like it, and unsubscribed--game ran great, though.
After hearing about the major changes in the game, I decided to give it another go. Upon beginning playing, the fan on my video card--I'm pretty sure it's my video card--starts to spin faster than I have ever heard it spin. It keeps getting faster until, without warning, my computer shuts down completely, which I assume is the system trying to protect itself. Now, while this could very well have something to do with overheating or poor ventilation, part of me doubts it. After all, I do run gpu-intensive games such as Witcher 2, Starcraft 2, Dungeon Siege III, and others without a hitch, Final Fantasy XIV seems to be the exception.

I tried playing a few games after this problem in order to check if my card was dying, but there weren't any problems--in fact, my video card remained completely quiet.

Help!