CMOS batteries allow you to store basic settings on your laptop. If you notice certain features on your computer do not operate correctly, such as the computer clock, you may have to replace your CMOS battery. This battery sits on the interior portion of your machine and measures about the size of a dime. If you have a screw driver and know how to work with your hands, you can replace the CMOS battery on your Acer Extensa computer.
Open the screen of your laptop until you can view your keyboard clearly.
Find the bar that consists of plastic on the upper portion of your keyboard. Place your screwdriver on one end of this bar and slowly ease it up until you can grab its edge with your finger.
Pull the opposite side of the bar in the upward direction with your screwdriver. Then, ease out the whole bar.
Take out the screws on the side portion of your keyboard. Pull your laptop keyboard upward and put it on a soft surface such as a bed or pillow.
Take out the four screws from the steel plate, which covers the motherboard of your computer, and take off this plate. This allows you to view the CMOS battery, which sits on the lower right portion of your motherboard.
Pull the CMOS battery up from the motherboard and take it off. Insert a new CMOS battery, which you can buy at a local computer store. Put the parts of your computer back in the same manner as you took them off.