CMOS CHECKSUM ERROR - DEFAULT LOADED

Issue

When starting your PC, the following error message is displayed:

CMOS wrong
CMOS MEMORY size WRONG 
CMOS Checksum Bad
CMOS checksum error defaults loaded
Warning! CPU has been changed please re-enter cpu settings in the cmos setup and remember to save before quit!

You are prompted to:

Press F1 to resume
Press F2 to load default values and continue

This is due to the fact that the CMOS, which contain data related to the BIOS, has been reinitialized and that your PC has been reset to factory settings.

Solutions:

Reinitializing the BIOS

Before making any costly maintenance try to reinitialized the BIOS.

Change BIOS battery

If the problem persist this may be due to the fact that the battery powering the CMOS (when the computer is shut down allows the CMOS to store information), is depleted.

The CMOS battery is a small pin found on the mother board, you can refer to the manual provided with your motherboard to change it or have the nearby computer technician change it for you if you don't want to risk any damage.

Replacing the battery of your motherboard (CMOS battery)