No administrators on my computer

So I was selling my computer to my grandmother, and my dad took it over to her house to set it up. He somehow managed to completely lock everything down. He created an account for her, but we never once were able to log into it. But he also deactivated me as an administrator.

So now I have my computer back, and I am trying ot set up the accounts, but I cannot do anything as I am no longer an admin. From what I have gathered, im up the creek without a paddle!

Please tell me I am wrong. How do I create an administrator account without an admin accoutn already in place?

Why not just do a clean install and give grandma a fresh start? BTW, have you considered asking your dad to buy it from you and then just giving it to grandma?

Well she was about to buy one for $900. Im selling her my new one that I bought for $900 for only $250.

As for clean install, we dont have any discs. I created an account for her, was happy to leave it at that as she just wants a computer to play majong and farmville. Dad then decided he needed to delete my account and give her admin, and yeah... this is were we are at now.

A clean install will be the final option, but I have no idea where to go to find my CDs.