Like most computers, the Dell Dimension 5000E contains a small battery that provides a charge to a small rewritable memory chip called the complementary metal-oxide semiconductor (CMOS). When the computer starts up, the system firmware---called the basic input/output system (BIOS)---obtains from the CMOS basic system configuration data, such as the date and time and any motherboard timing settings you have changed. If the battery that provides a charge to the CMOS is dead, the motherboard loses this configuration every time the power is turned off. Replace the CMOS battery in your Dell Dimension 5000E if you find that you must re-input the date and time whenever you turn on your computer.
Shut the Dimension 5000E down. Unplug all of the cables that are connected to the computer tower, and bring the tower to a sturdy work surface. Lay the tower so that the left side faces up, showing the removable panel.
Push the release lever on the top of the computer tower back to release the side panel, then swing the panel open from the top of the tower to the bottom. Remove the panel and set it aside in a safe location.
Grasp the installed coin cell battery with your finger and thumb and gently wiggle it until it is freed from the battery compartment. If you are unable to remove the battery with your hand, carefully pry it out with a small tool that does not conduct electricity.
Push the replacement battery into the compartment so that the positive side faces up, showing a "+" sign.
Align the bottom of the side panel with the Dimension 5000 tower and swing it closed. Push the release lever at the top of the tower back, then pull it in to lock the side panel into place. Return the computer to its original location and replace the cables.
CR2032 batteries are available from many electronics stores. Ask an employee for help if you have trouble locating one.