Hi Kirsti,
First of all, just explaining for everyone who may interested, the bios password and the administrator passwords are 2 completely unrelated things.
The only way to change your admin password is either through the rescue manager (a text interface that you can bring up by pressing F2 at boot up) or through the system manager (that you can reach when the unit has gone into graphical mode). To change it you either need to know the current one, or you ask us to reset it by sending us a special token from the rescue manager. We only change it if we are satisfied of your identity, so that not anyone can ask for resetting it behind your back.
Now the bios settings, these give access to the boot order or PXE settings. They are protected by a password, specified in one of the parent posts, and you can change it by going to the bios menu (press del during the very first stages of boot up). There is an item in the main menu to change that password. That password doesn't protect your sessions from being edited, it just protects the hardware settings. If you want to protect your sessions, have a look at the following post:
http://forums.netvoyager.co.uk/viewtopic.php?f=6&t=65Tell me if you need more directions.
Ben