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Shut down the computer
If a program became unresponsive and you weren't able to quit it via any other method, shut it down. This method is more helpful to laptop users than to desktop computer users, because desktop computers have a dedicated restart button.
To force-shut-down the computer, press and hold the Power On/Off button until the cooling fans stop working (which should be in around 15-20 seconds after you have pressed the power button). Turn it back on after a minute or two.