How to enable the Administrator account in Windows Vista (Ultimate Edition)

Open Control Panel, go to Administrative Tools and open Local Security Policy.
Then open Local Policies and expand the Security Options item,right click on Administrator
account status select Properties, click on the Enabled option and then click on OK button.

After you have enabled the Administrator account you need to set a password for it.
In order to do that, follow the steps below:
Open Control Panel, go to Administrative Tools, Computer Management and expand the
Local Users and Groups item. Now right click on the Administrator account and select Set password

Now that you have set a password you can logoff and then logon as Administrator.

Enjoy :)