Okay, right-click your desktop, and select Nvidia Display, and the name of your card (it should appear next to it). There should be a little menu at the left, see if there is something called "Temperature Settings" and click that. If there isn't, try to download RivaTuner (http://downloads.guru3d.com/download.php?det=163
) and see if it'll tell you.
By the way, I was (and still am) talking about the video card temperature, not the processor temperature. I'm sure the processor is fine. This definitely sounds like a video card overheating problem or something, and since you have the silenced version, I'm inclined to think that's what it is.