Administrator Account
How do I enable the built-in Administrator account?
kadaitcha.cx does not recommend enabling the hidden Administrator account in Vista, however if you really must...
Click Start and type cmd in the Start Search box, and then right-click cmd.exe in the Programs list. Select Run as administrator:
In the command prompt, enter the following command:
net user administrator /active:yes
If you log off you will see the Administrator account is now a logon option. To disable the Administrator account, enter the following command:
net user administrator /active:no