Okay, so here is how my question comes about... I have already searched and could not find links to other threads.. I bought a G4 desktop from a guy on craigslist about a week ago and I want to upgrade from 10.3.9 to the newer 10.5. He has an administrative account on the computer and whenever I try and load the 10.5, it asks for his password. I called the guy wondering what his password was and he told me. I tried entering that in and it will not work. Now the guy will not answer his phone or his e-mail address. I know he was the original owner because of the information on the computer and the name on the business card he exchanged for mine. I would really like to upgrade my OS but I need to know how to go about reseting the computer to erase 100% of everything on the computer. Can someone please help me, I am new to Mac and I don't really know what to do!!!