The CMOS battery allows the motherboard to retain its settings when the computer is turned off.
There is a battery that protects your Dell Latitude settings when it is not powered on called the CMOS battery. When the CMOS battery starts to go bad, your computer may behave erratically, turn itself off and/or display error messages about the system not matching the configuration. Changing the CMOS battery is not difficult, and, if you change it before it dies, you'll save settings that will be lost if it loses all power.
Instructions
1. Turn the computer off and disconnect the power cord from it.
2. Disconnect the battery from the computer.
3. Drain any power left in the computer by pressing the power button.
4. Turn the computer over, and lay it down.
5. Put on your wrist strap and connect the end of it to a metal surface.
6. Unscrew the cover to the memory module. On most Latitude models, this is a small cover beside the larger hard drive cover.
7. Locate the guide on the battery compartment, and gently pry the battery out with the plastic toothpick.
8. Insert the new battery, positive (plus) side up, under the battery clip and push the battery into place.
9. Screw the cover on and reattach the battery to the computer.
Tags: CMOS battery, Dell Latitude, settings when, Turn computer