Windows Server 2003 allows you disable the the local Administrator account to provide an additional level of security. It even defaults to disabling the local Administrator on the destination computer of a RIS (Remote Installation Services) install.
To log on as the local Administrator after you disable that account:
01. Restart your server.
02. After the POST (Power On Self Test), press F8.
03. On the Advanced Options menu, use the ARROW keys to select Safe Mode and press Enter.
04. Select the operating system that you want to start and then press Enter.
05. Log on as Administrator. If prompted, select an item in the Why did the computer shut down unexpectedly list and press OK.
06. Right-click My Computer and press Manage.
07. Expand Local Users and Groups.
08. Select Users.
09. Right-click Administrator in the right-hand pane and press Properties.
10. Clear the Account is disabled box and press OK.
11. Restart your server and log on normally as Administrator.
NOTE: You can also log on to the Recovery Console while the Administrator account is disabled.