My computer unexpectedly shuts down while playing some games. I'll play for about 5 minutes, then I hear a beep and the computer immediately shuts down. I thought that maybe it was because I was putting too much strain on my gpu (nvidia gtx 230), so i tried lowering my settings, but that changed nothing. This only happens for some games, and occasionally, the computer will not shut down. I am using an hp dv7t laptop with a core i7 720 quad core processor and 4 gigs ram.. Is this a hardware or software issue? And is it fixable/ avoidable?