I'd agree on MOBO, however if you want to take some extra steps here are a few angles you can try in whatever order makes sense. If you have a
Kil-O-Watt it may be helpful to see what happens to the wattage when you boot a game - does it spike too high?
- Try a simple memtest. One full pass.
http://www.memtest.org/
- Try a simple processor test. Normally used to test stability on overclocking.
http://files.extremeoverclocking.com/file.php?f=205
- Try FurMark - would be interesting to see if OpenGL runs fine.
http://www.ozone3d.net/benchmarks/fur/
- Try Heaven Benchmark - should definitely fail.
http://unigine.com/products/heaven/
- Try taking the battery off the MOBO to cut power/reset it completely.
- Try re-seating the processor. I run an old i7 that I generally clock at 4.1GHz (stock clock is 2.67GHz). Ever so often, my computer will fail to boot and I have to set it back to stock rating to get it going. The only way I've gotten around this is to re-seat the processor, overclock - works fine after for months on end. Have had to do this 3 times so far. Never underestimate re-seating!
- Try running Furmark and Prime64 at the same time. This will cause your computer to suck up as much power as it possibly can. Good way to load the PSU.
Be wary of heat levels when using Furmark and Prime64, particularly Prime64.