Here is how to turn off a Windows 8 PC Computer. The Start Menu is gone, and there is no visible power button on the Metro or Desktop. To turn off your Windows 8 PC computer, put your mouse pointer in the upper right corner, and when the side menu pops up, select the gear icon. You will see a power button icon. Click it and choose Shut Down from the menu. It is easy to turn off a Windows 8 PC computer once you know now, but they did a good job of hiding the power button.