Windows 7 - New custom built PC will not turn off

Hi,

I recently built a new computer for my brother, and as of yesterday, the system will only power on, and the only way to power it off is by either turning off the PSU or unplugging the power cable, neither of which I feel particularly comfortable doing.

When the computer's power is off, the power can be turned on by pressing the power button. However, when the computer is on, pressing or holding in the power button does nothing. If the shutdown option is chosen from the start menu, the computer will go through the standard shutdown sequence, and the monitor will go to sleep, but the fans in the computer will continue to run. If the power button is pressed at this point, the computer will act as if it is turning on normally and boot into Windows properly.

This problem started late last night. Prior to then, the computer would shut down and power off normally. No hardware changes were made to the system between the last successful power down and the time in which this issue started.

System hardware:
OS: Windows 7 64-bit
RAM: 4GB DDR3 (Two 2GB sticks)
Processor: AMD Phenom II X2 560 Black Edition (3.3 GHz Dual Core)
PSU: Cooler Master RS-460-PSAR-J3
Motherboard: ASUS msq-m4n68t-mv2(b)
Hard Drive: Seagate Barracuda ES.2 500GB
GPU: NVidia GT250

With a new build, that's always a potential problem. Please reseat your memory and any pci-e card you have (with the computer unplugged). Also check all power connections to the motherboard, drives, etc.

If this does not work, remove all cards and memory and try starting the pc - just to see if it locks up. Of course it can't get far, but another diagnostic step.

Let us know how that goes.

** EDIT ** Also, your power supply may be slightly underpowered. Also, did you change anything on the bios? OC?

Along with what Lemur has suggested, I would check the power switch connection on the case to the mobo. It maybe something as simple as having the connection backwards. The pin connection flipped/flopped.

Open control panel and go to power options and then to "Choose what the power buttons do". Make sure "When I press the power button" is set to "Shut Down" and not hibernate or sleep. Also check the BIOS, there should be a setting to shut the PC down if you hold the power button for 4 seconds or instant off. I set mine for the 4 second delay so it doesn't interfere with the windows power down option.

+1 on this. I think default it's set to do nothing or sleep.

Thanks for the replies, everyone. I'll test out some of these fixes when I have a chance tomorrow and report my findings here.

The only thing I have ever changed in the BIOS was the default boot drive for when I was installing the OS.

On all of the motherboards I've seen, the power switch connection is not polarized.

The control panel setting will do nothing. If you manually choose shutdown form the start menu there is only one command that is given.

While the power button itself might be at fault (you can test this by shorting the + and - pins on the mobo with something metal)
It might also be a power supply issue. If the power supply doesn't drop the voltage sufficiently the motherboard will never give the shutdown sequence, and a common symptom is a half and half state.

You are correct, the power button and reset button are single contact momentary switches. It doesn't matter which way the plug goes on, the two pins are shorted together when the button is depressed and an open circuit when its released.

Sorry for taking so long to post this, but I have solved the issue. Turns out one of the PSU's motherboard connection cables were loose. Got it plugged in all the way and now everything works perfectly fine.

My guess is that it probably got knocked loose from being transported between locations. I don't normally do this, but had to due to some maintenance equipment was somewhere else and so on..

Thanks for all the help, everyone!