Cause - CMOS battery has gone bad
1. When replacing the CMOS battery in the ZPC, be sure the External Power Supply is unplugged and no accessories are plugged into the unit.
2. Carefully remove the 5 bottom screws and the 2 back screws to remove the keytop.
3. Once the unit is open, simply remove the bad battery and replace it with the new one. We use a standard 3V Lithium battery that can be found in most stores.
4. When everything is put back together, be sure to press the CMOS reset switch on the side of the unit.
5. Boot up the machine and repeatedly press the delete key to enter the CMOS Menu.
6. Choose to Load Optimized Defaults, then press F10 to save and exit.
The PC will now boot up normally.