When a workstation/server is joined to a domain, it hides the checkbox for “Users must enter a user name and password to use this computer” from the userpasswords2 control panel.
To get autologon working, you need to restore this functionality by running the following from a command prompt to add a registry key:
reg add “HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon” /v AutoAdminLogon /t REG_SZ /d “1” /f
Once that is done, it is recommended to run the following from a command prompt to add a registry key to specify the default logon domain:
reg add “HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon” /v DefaultDomainName /t REG_SZ /d “domain” /f
After both registry keys have been added, launch the userpasswords2 (Start->Run->control userpasswords2) and click “OK.” to set the username/password you want to autologon with.
Please note: This tip also works for Windows 7 and Windows Server 2008.