I have just rescued a Imac G3 for my son to play around on that the school It department were recycling. Unfortunately it has been set to start on  an admin. password ser in the dawns of time and unknown to the current staff. I am unfamiliar with mac and unsure how to get it up and running again. I have tried to reinstall with the same os it has on board, 9.2 that I have downloaded, but no joy. Can anyone help? I am a pc kind of a guy and only dabbled briefly with mac at tcoll.

cheers in advance