Windows 7: Computer Shutting down and turning on.

The power button on the case is a momentary contact normally off switch. The contacts are only closed (on) while the switch is depressed. It is conceivable that its faulty and the contacts are making contact , maybe intermittently, when the switch isn't being pushed. That could cause the PC to turn on by itself. If windows is set to shutdown when the power button is depressed (power options) it could also cause the PC to shut down gracefully. The case reset button works the same way as the power button. If you get your motherboard back and the problem is still there unplug the cable for the case power button and swap it for the reset button. Leave the power button unconnected. It you problem goes away it was the case power button. I'm more inclined to think its probably the circuit on the motherboard that the power button connects to that is faulty. Only time will tell though.

Hi,

Thanks for your reply.

I have received a new replacement motherboard and the issue is still the same. The only thing now I can think of is to change the case and the power button must be causing this issue?

Yes, try a different case/replace the button. I think there is a way to just disconnect the button from the motherboard. You just won't be able to turn you PC on but if it doesn't turn on by itself, that means it was because of the button.

Then i think your power switch is the problem,what you got to do is,try to open your front Case,locate your switch cable,it has 2 cable connected to your switch button.cut the wire,it should be 1 red and 1 black or 1 white and 1 black or maybe in green color.try to short the wire,just touch it for about 5 millisecond.i means touch the wire together,if your motherboard come to life,just replace the switch on button and the wire. hope this solved your problem.