Windows 7 Woops :O im in trouble

[cameronfilm]

I have a school laptop which had windows 7 installed and my account "Cameron" is an administrator on the windows 7, however the permissions in the hard drive are set to some other admin account. I changed the owner of the files through the permissions to "Cameron" from some other random admin account. Then, some icons are dissapeared such as the windows live messenger icon and the adobe reader icon. When i right click and press find icon it says cannot find RootSystem or somerthing.
also when i tried to isntall a Dell driver yesterday it said i needed permission or somerthing.
ive really stuffed something up.
can anyone help