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How to Reset CMOS

  1. Unplug PSU power cable from wall, this ensures no power is going to the PC.
  2. Remove CMOS battery. This is a small ‘watch battery’ in your motherboard (see below).
  3. Press and hold PC power button for 30 seconds, this clears out any remaining charge in your PC.
  4. Reinsert the CMOS battery, reconnect power and try starting the machine.

What does the battery look like?

cmos battery