HP EliteBook User Manual page 85

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 73