Enable hidden Administrator account Window 7

Try this, 1. Open a elevated command prompt. Click on All Programs and Accessories, then right click on Command Prompt and click on Run as administrator.
2. To Enable the Hidden Built-In Administrator Account -
A) In the elevated command prompt, type net user administrator /active:yes and press Enter.
3. To Disable the Hidden Built-In Administrator Account -A) In the elevated command prompt, type net user administrator /active:no and press Enter.
4. Close the elevated command prompt.
5. Log off, and you will now see the built-in Administrator account log on icon added (enabled) or removed (disabled) from the log on screen