Unable To Delete/demote Account

My son changed a standard user account with parental controls to an administrator account by downloading a program off the internet. He went to Offline NT Password & Registry Editor and downloaded cd080802.zip under the bootdisk submenu. Our attempts to correct the problem have failed. We've tried deleting the account through Control Panel and command prompt. We've tried making the account inactive through command prompt. Even when we type in "net user *** " all we get is "The syntax of this command is: ..." like the account is inaccessible. You don't get the "user name could not be found" message that you would if you typed in an invalid user name but you don't get the account information that you normally would either. We've tried system restore but the account is still set as administrator.