Once you join a server to a domain, Windows will automatically delete the AutoAdminLogonvalue from the HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogonregistry key. This causes the userpasswords2 control to hide the “Users must enter a user name and password to use this computer” check box.
Here's how to get the missing checkbox back and configure AutoLogon:
reg add “HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon” /v AutoAdminLogon /t REG_SZ /d “1” /f
You may find that you need to configure the default domain, as well. If so, enter the following (all on one line) at an elevated CMD prompt:
reg add “HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon” /v DefaultDomainName /t REG_SZ /d %USERDOMAIN% /f
When the computer starts up the account you specified will be logged in automatically. Note that the password is encrypted on the computer.
This tip works for Windows 7, Windows 8, Windows Server 2008, Windows Server 2008 R2, and Windows Server 2012.