HP ProBook 4320s Notebook-PC - Manual (Page 95)

If the computer is unresponsive and you are unable to use the preceding shutdown procedures, try the
following emergency procedures in the sequence provided:
● Press ctrl+alt+delete . Then, click Shut Down > Turn Off.
● Press and hold the power button for at least 5 seconds.
● Disconnect the computer from external power and remove the battery.
Shutting down the computer 83