Restarting the computer by turning the power switch off and then on, or by shutting down the computer, turning it off, and then turning it on again.
If you perform the first type of rebooting, open files will not be properly closed and data can be lost. However, this method ensures that memory is cleared and devices are properly reset.
An example might be when you reconfigure the settings of a legacy modem using the modem utility in Control Panel.
You might find that you must cold boot your machine in order for the new configuration settings to fully take effect.