ASUS motherboards, manufactured for both Intel and AMD processors, are a popular choice for custom-built computers. The motherboard's battery is a flat, round 3-volt lithium battery. This battery, which is installed in a special motherboard socket, powers up CMOS (complementary metal--oxide--semiconductor). CMOS is an integrated motherboard chip that stores current BIOS (Basic Input/Output System) settings, such as system date and time. A CMOS battery may last for many years, but eventually dies. So you need to replace it.
Purchase a new CMOS battery available from many retailers (see Resources section). ASUS motherboards typically use a lithium CR2032 battery.
Turn off the computer.
Remove the computer case side panel.
Lay the computer on its side.
Find the CMOS battery that is situated in the socket approximately in the centre of the motherboard.
Touch an unpainted metal part of the computer case or another metal surface to discharge static electricity.
Lift the CMOS battery out of its socket, using your fingers, and set it aside.
Insert the new lithium battery gently into the socket. Make sure that the battery's positive pole, marked with a plus sign (+), faces up.
Move the computer into the upright position and close the side panel of the computer case.
Press the "Power" button to turn the computer on.