The Complimentary Oxide Semiconductor, or CMOS, battery in your Acer Aspire 1500 is a small, round battery--much like the battery in a wristwatch--that powers various basic internal components of your computer while it is turned off. For example, your computer's internal clock is powered by the CMOS, so if you turn on your Aspire and the clock display isn't functioning, chances are you need a new CMOS battery. To access this battery, you have to disassemble your computer to gain access to the motherboard.
Turn off your Acer Aspire 1500 and remove any cables or peripheral components from the device, including the power cable.
Push the battery release button located on the side of the battery compartment up and remove the battery.
Gently remove the disk drive by sliding it out of its compartment on the side of the computer.
Turn your Acer Aspire 1500 over on a flat surface and use your Phillips screwdriver to remove all the screws from the hard drive and Wi-Fi compartments located in the middle of the underside of the computer. The hard drive compartment is the largest on the underside of the computer and the Wi-Fi compartment is marked Wi-Fi.
Remove the hard drive and Wi-Fi compartment covers. Remove the thick, rectangular hard drive by sliding it out of the compartment and unplug the Wi-Fi antenna cables from the thin rectangular Wi-Fi card sitting in the compartment.
Turn your Aspire right-side up and open it so the screen is facing you. Remove the long plastic bezel (frame) from the top of the keyboard by lifting it up at the corner and gently prying it off with the tips of your fingers. This will expose the two screws that secure the keyboard to the computer.
Lift the keyboard up with your fingers and place it face down on the front of the computer. Unplug the single connector ribbon running from the computer to the back of the keyboard, then unplug the single cable that runs from the computer to the touchpad. Unplug these cables from the back of the keyboard and touchpad.
Lift the internal metal housing up from the back of the computer, then lift it up from the sides and gently pull it up and separate it from the laptop. Set the metal housing aside.
Locate the CMOS battery in the corner of the green motherboard that should be visible after you extract the metal housing. It is a small circular, silver battery and will be labelled "CMOS." Lift it from its small compartment and replace with your new CMOS battery (available from your Acer retailer or online). Make sure your new CMOS battery is an identical model to the one you removed. You can match the battery models by the etchings on the front or you can consult your Acer retailer.
Reassemble your Acer Aspire 1500 in the reverse order you took it apart.
It's a good idea to wear an ESD (Electrostatic Discharge) wristband when working on the internal components of your Acer Aspire 1500 in order to prevent damage to your computer from static electricity.
Working on your Acer Aspire yourself may void any warranty you have on the device.