Alternatively called a cold start, hard boot, and hard start, cold boot is the process of powering on a computer from a powered-off state. For example, when you first turn your computer on after being off for the night you are cold booting the computer.
A cold boot is never called a cool boot.
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 turns 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 that is on (is warm) without turning it off.