I just got my first Mac from a second hand store and it runs great and I seem to have no problems with it, but it is logged in as the previous owner and they aren't the administrator. So, I can't download and install anything because I don't have the password or the 'rights' to do anything without the administrators permission. How could I go about resetting the settings, or anything else, so I could be the administrator? I'm able to go about everything else, I have just been making sure not to log out to whoever the computer automatically logs in to. I don't know anything about Mac's at all, I've always had PC's. HELP PLEASE