Like most computers, the Dell Latitude D505 laptop uses an internal memory chip called a complimentary metal oxide semiconductor (CMOS) to save the basic hardware configuration of the machine. To save the configuration, the memory chip requires a constant electrical charge, which a small battery supplies when the computer is turned off. If you make a mistake when making changes in the motherboard set-up utility or configure a BIOS password and forget it later, you can reset the CMOS of the Dell Latitude D505 by temporarily removing the CMOS battery.
Shut the Latitude D505 off. Close the screen, remove all cables connected to the computer and turn it over so that the screen faces down.
Push the tab on the edge of the battery pack in while simultaneously reaching under the edge of the tab with your finger. Lift the battery out of the bottom of the Latitude D505. In the outside corner of the empty battery compartment, you will see a small plastic door with a release tab that looks similar to the one for the primary battery.
Push the release tab for the plastic door and pull it out of the corner of the battery compartment. Under the door is a small green battery with a twisted cable leading to a plastic connector.
Pull the plastic connector to disconnect the Latitude D505 CMOS battery from the motherboard.
Turn the Latitude D505 over, reconnect the power cable and open the screen. Turn the computer on and allow Windows to load, then turn the computer off again. Turning the computer on with the battery removed clears the CMOS memory.
Reconnect the CMOS battery, replace the cover and reinstall the primary battery.