How do I perform a hard reset on my LabQuest unit?

Note: Do not use a Hard Reset except as a last resort such as when both the screen and hard keys are not responding. This is equivalent to turning off a computer by yanking out the power cord instead of shutting it down.
For other options, see:
     TIL 1777: How do I reboot or reset a LabQuest?
     TIL 1688: Original LabQuest Troubleshooting and FAQs (Full List)

There is a small gray button inset in the back of the LabQuest which is used to perform a hard reset. The button is located just below the stylus sleeve and can be depressed with the tip of the stylus.

To perform a hard reset, put the stylus on the reset button, then look at the face of the LabQuest. When you press the reset button, hold it down for ten seconds. The blue power light should turn off while you are depressing the reset button.

If the blue power light goes off, but the unit does not reset, follow the instructions for removing and replacing the battery. See:
TIL 2189: How do I remove or replace a LabQuest battery?

If the blue power light does not go off at all, please see:
TIL 2087: LabQuest will not reset when I depress the reset button.

See also:
TIL 2077: Original LabQuest Battery Troubleshooting and FAQs