This video shows how to open the case and then remove the password from the BIOS of a Dell Optiplex GX280.
1. Shut down the computer.
2. Remove the power cable.
3. Open the case.
4. Remove the CMOS battery.
5. Remove the PSWD jumper located near the motherboard’s power connector.
6. Put the CMOS battery back in.
7. Close the case.
8. Reconnect the power cable.
9. Start the computer and use F2 to go into the BIOS settings.