Parental Control Problem

Hi, Sure hope someone can help me. I purchased an Acer Aspire One Netbook for my 12 year old and set up parental controls for him. I set time limits for log on for him. Yesterday I logged on as administrator and had to step away for a few minutes and Junior changed the settings to make himself administrator and me as a user. I can log on to his computer at any time but to change the settings I cannot give permission using his password even within the time limits I put him under. How can I change this back without having to pay to have it done at the shop.
Someone must have run into this problem before, please help!

If he's changed to an administrator, you should be able to change everything back when he's logged on.

This issue has been resolved! A friend called and told me to reboot in Safe Mode and I was able to change everything from there. Thank heavens! No costly repair bill.