Pick up HWMonitor. Set it up to record info. It will say what you cpu, and gpu temps and voltages where when it crashed.
http://www.cpuid.com/softwares/hwmonitor.html
Also type: dxdiag in your search box in windows. Run it then paste the results here. It will be a huge file but someone might find the problem through that.
Also run a memory test to make sure that is ok. Personally I would go with something overheating. but really hard to tell without some kind of diagnostics.
One last thing. Are you overclocking anything and if so what, to what level and the vcore.