Powermac g4 admin root password help

Hello,

I recently acquired a Power Mac G4 digital audio which is running 10.3 Panther. I was planning on doing some video editing with it using FCE 4.0. The only problem is I need to be running 10.4 or later. My only problem is, I can't install 10.4 because I dont know the administrator password, and I have no means of contact with the original owner. I also dont have the original install disks. How could I reset the admin pass so that I can install new software?

Thanks