Get one of the two applications I've mentioned above.http://www.almico.com/speedfan.phphttp://event.msi.com/vga/afterburner/download.htm
Speedfan's probably a little easier to use.
Do one of the things that makes it crash while watching the GPU temperature in either application. If it goes over 75C, it's probably the cause of the crash. Check the CPU temperature as well: if it's over 65 or 70, it could also be the culprit.
It's nice that the ambient temperature is so low, but that doesn't rule out an overheating processor or GPU.