school hacking

hey at school today i managed to somehow put my username in the admin group and i made a username, but the problem with this uname is that it can only be used on the com-uter that it was made on (by this i mean at the logon screen we have a choice of which domain we want to log on to, the curric domain, library, and then the pc in which i am sitting in front of). So i just wanted to ask if any of you people knew anything about it. note when I logon normally a logon script apears and we also have mySQL for some reason

I doubt it's really MySQL. Explain how you added yourself to the group.

You likely only added yourself to that local computer, and you'd need access to the network server to get on the true network.