Forgotten Admin Password

I have been a happy powerbook user for nearly a year now (couldn't be happier!!) Recently purchased an eMac to complement the powerbook back at home. I opened it up and organised it my way some months back and then packed it up as i was moving house. It has lay unused since then, i'm now moved in and ready to get it all up and running but have completely forgotten the password i saved as my administrator! I've tried everything!!! What do i do?????
Thanks for your time in advance!