Alternatively referred to as a cold start, hard boot, and hard start, cold boot is a term used to describe the process of turning on the computer after it has been powered off. For example, when you first turn your computer on after being off for the night you are cold booting the computer.
How to cold boot a computer that is running?
When a computer freezes or gets into a deadlock, it cannot be restarted (warm boot); it needs to be cold booted. However, today's computers are designed to prevent the computer from being mistakenly turned off while it is running.
To perform a cold boot on a computer that is running press and hold down the power button. After continuing to hold the power button down the computer will turn off after a few seconds. Once the computer is off wait a few seconds before turning the computer back on.
Cold boot vs. warm boot
The opposite of cold booting is warm booting, which is restarting the computer on after the computer has been on (is warm).