In versions of Windows before Windows Vista, the Administrator account wasn't hidden, and many people used it as their main or only account. This Administrator account had full rights over the computer.
In Windows Vista, Microsoft changed that. In Vista, the Administrator account is not subject to UAC, but normal administrator accounts are. So the Administrator can make any changes to the system and will see no UAC prompts.
Turning on the Administrator account is straightforward. First, open an elevated command prompt by typing cmd into the Search box on the Start menu, right-clicking the command prompt icon that appears at the top of the Start menu, then selecting Run as administrator -- or just use the shortcut you created in the previous hack.
Then enter this command and press Enter:
Net user administrator /active:yes
From now on, the Administrator account will appear as an option on the Welcome screen, along with any user accounts you may have set up. Use it like any other account. Be aware that it won't have a password yet, so it's a good idea to set a password for it.
If you want to disable the account and hide it, enter this command at an elevated command prompt and press Enter:
Net user administrator /active:no