Changing account limitations on OS X ?

I was given a iBook G4 by my school, and my account is restricted

  A while back, by some fluke, I was able to use applications, but when I restarted, It reverted back to the same state, anyone know if I did anything by accident that I can exploit to do this again ?

If you can get an OS X install CD, you can change the adminstrator account password.