i've had an issue like this on an old computer of mine (well, not old, one of the previous comps)
It used to run fine on max level, then blue screen & hard resetted.
It was , as Slave2school mentioned, a RAM issue.
I had to go into the BIOS & downclock the ram, because else it'ld overheat pretty fast.
I ended up replacing the ram & everything worked fine for 4 years
do a memtest & see what it tells you
or try downgrading the ram speed in the bios.