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Administrator Account does not Appear on Welcome Screen
http://www.vistaarticles.com/articles/226/1/Administrator-Account-does-not-Appear-on-Welcome-Screen
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Published on 12/10/2006
 
You notice that the administrator account does not appear on the Windows Vista Welcome screen.

Administrator Account does not Appear on Welcome Screen

By default, the following conditions are true in Windows Vista:

The built-in administrator account is disabled.
The built-in administrator account cannot log on to the computer in safe mode.

In some cases, Windows Vista may determine, during an upgrade from Microsoft Windows XP, that the built-in administrator account is the only active local administrator account. In this situation, Windows Vista leaves the built-in administrator account enabled. Additionally, Windows Vista puts this account into Admin Approval mode.