Logon Vista As Administrator

Enable the Administrator Account
Open the command prompt with Administrative privileges by opening the Start Menu, and typing cmd in the search box,
and then press Ctrl+Shift+Enter or click the Start orb, All Programs, Accessories, right-click Command Prompt and select Run as administrator.

Type the following in the command prompt and press Enter after:
net user administrator /active:yes

Restart your computer and logon as Administrator.
Note: You might want to set a password for the administrator’s account for at least a little protection.

Disable the Administrative Account
To disable the Administrative account run the Net User command demonstrated above while logged on an account with administrative privileges
but not as the Administrator account and replace yes with no.