A BIOS password prevents access to a computer by keeping the operating system from loading if the password is not entered by the user. If your computer is locked by a BIOS password, you can neither access the BIOS nor access your system if you do not have the password. To clear the BIOS password on your Latitude D620, you can remove the CMOS battery from your computer's system board to reset the BIOS memory.
Shut down your computer and remove all peripherals from the machine. Unplug the AC adaptor and remove all batteries from the computer.
Open the computer display to 180 degrees. Insert the plastic scribe or flathead screwdriver into the notch at the top right corner of the laptop and gently pry the plastic hinge cover away from the computer. Working from right to left, pry the hinge cover away from the computer case and set it aside.
Unscrew the three screws that hold the keyboard to the case. Gently lift the keyboard up from the computer. Disconnect the keyboard ribbon cable from the computer using the pull tab and set the keyboard aside.
Unplug the CMOS battery connector located at the top-centre of the system board. Gently lift the corner of the plastic mylar battery cover up and remove the battery from the slot. Let the laptop sit for thirty to sixty minutes to ensure that all power is drained from the machine.
Replace the CMOS battery beneath the mylar battery cover and reconnect the CMOS battery connector to the system board. Plug the keyboard ribbon cable into the system board and screw the keyboard back onto the system board.
Replace the hinge cover by gently pressing it into place from left to right. Plug in your computer's AC adaptor and any peripherals you removed. Start your computer; the BIOS password will be clear and you can use your computer normally.
If the BIOS password does not clear, repeat the procedure, but let the computer sit longer. The capacitors on the system board need to drain completely for the password to clear.
Working on a computer connected to a power supply is dangerous and can cause damage to the system board. Make sure to unplug the computer from all power sources before working on the machine.