Enable the Built-in Administrator Account

Use the Local Users and Groups MMC console
Change the properties of the Administrator account by using the Local Users and Groups MMC console.

1. Open the MMC console and select Local Users and Groups.
2. Right-click the Administrator account and select Properties. The Administrator Properties window appears.
3. On the General tab, clear the Account is Disabled box.
4. Close the MMC console.

Administrator access is now enabled.

Disabling the Built-in Administrator Account

Note: Original equipment manufacturers (OEMs) and system builders are required to disable the built-in Administrator account before delivering the computers to customers.

Run the sysprep /generalize command

When you run the sysprep /generalize command, all account information is removed from the computer, including the built-in Administrator.

The next time the computer starts, the built-in Administrator account will be disabled.

OR

Use the net user command

net user administrator /active:no