Has it ever posted past the samsung logo? Have you successfully booted into the bios? As everyone mentioned it does sound heat related. Check out fans and vents to see if there is anything obvious. Normally most PC's nowadays have thermal event limiters. Well. They'll shut down if they get too hot to prevent any damage to the CPU and other components. You'd be surprised the temperature you can safely get them up to. Have a blast at the vents and fans. Wait a while for the system to cool. Completely. And then try boot into the bios. If you successfully get into it and it doesn't switch off then you've solved the heat issue. Then if it doesn't boot. Or hangs on windows loadup etc. Try safe mode. See how you get on. . . Sorry if that sounds a bit methodical. That's what working in IT does to ya. Turns you into a machine yourself. Lolls