A.
By default, new Vista installations have the built-in Administrator account disabled with a blank password. If you want to enable the account, you need to set a strong password by using the Microsoft Management Console (MMC) Computer Management snap-in and clearing the disable flag. It's advisable to leave the Administrator account disabled, however, and use the Runas command to use Administrator privileges when required, as the figureshows.
If you log on as the Administrator account, then User Account Control (UAC) isn't implemented and the session will have full privileges.