I've completely messed up my Administrator Permissions... HELP

Hi guys,
I hope there is a solution to this that doesn't involve me completely wiping my hard drive but I am prepared to do so if required.
Recently I was setting up a user account for a friend so they could use my laptop and i accidently changed all of the Administrator Permissions.
Now I can't access my C Drive. I can't copy and paste, most of my programs won't boot properly because the permission to the C Drive were taken away.
I also can't access the User Account setting because I have been locked out of that too.
I know, I know... I've thoroughly messed it up but if anyone has any advice on how I might fix this problem it would be greatly appreciated.
Thanks so much.

In all honesty, you won't get this fixed properly. It will take you far less time to back up your data and reinstall Windows than to fiddle around with trying to change the permissions back.

I'm just going out on a limb here but shouldn't an earlier restore point fix the issue (which IMHO lies in certain registry entries)
Or how about a boot into safe mod, using the normally disabled admin to create a new admin account with proper rights?

-DG

Hi Ro76, sounds like you have a real problem, but I was not sure, reading your first post, if you had taken Administrator priveleges away from all the accounts, or if you had just removed all accounts access to the C: drive. If you have just removed the access to the C: drive, but still have Administrator accounts, you should explore the "Take ownership" tools. C:->Properties->Security->Advanced... assuming you have invested some time in setting up your system... Of course a reinstall is always an option. Every time I reinstall, I do it better.