Why does my computer not turn off?
To help protect a computer from being improperly turned off when it's running, the power button will not turn off a computer. If the computer is frozen or has other problems, press and hold down the power button without letting go for 5 to 10 seconds. Holding down the power button lets you turn off the computer.
While a computer is running, pressing the power button may put the computer into sleep mode. When a computer is in sleep mode, the power indicator usually flashes and pressing a button on the mouse or keyboard wakes up the computer.
If the computer is working fine and you want information about the proper way to turn it off, refer to the following article.
Finally, if you have a laptop computer and following the above steps does not turn off the computer, unplug the computer and remove the battery.