How to reset lost passwords of laptop BIOS?

One of my friends got an old laptop Dell Latitude D620 from one of her relatives. She has only the system password set in the BIOS Revision A08 in order to get to the user logon screen of the installed Windows XP Pro system.

Logging on to the laptop needs a system or administrator password before one can see the XP desktop user logon screen. The Administrator password of the installed Windows XP system dosen’t work.

I found there are other security passwords in the BIOS: Unlock Setup, Admin Password, System Password, Internal HDD PW and so on. How can I clear or reset all these passwords while I know only the System Password. Certainly I have no problem changing the System Password.