question on reformatting

I have a regular ibook lap top and i do not know my administrator password. I tried to reformat my computer with the 5 reformat discs that came with it, but when i put the first cd in and try to open it to start the reformatting process it says that i do not have the permission to open the software and that i need to get the password from the administrator, which I don't have. The last administrator does not remember there password....So I was wondering how can I override the administrator without the password so that i can completely reformat my computer and make myself the new administrator since the computer is now mine???

Put the install cd in and restart holding the C key. This will boot from the cd. When the installer starts, look in the menu and select "reset password". Change it to a password you will remember.