Connecting to Windows 2000:

Windows 2000 (Workstation and Server) doesn't allow you to automatically log on through a terminal session. This is an OS limitation. Automatic logon only works with Windows 2003/XP or later.

Server-side RDP settings can prevent automatic logon:

On the remote server (the one you want to connect to), open up the Terminal Services Configuration MMC (Windows 2003/2008) or Remote Desktop Session Host Configuration MMC (Windows 2008R2) from the Administrative Tools. Right-click on the RDP-Tcp connection and select Properties . Switch to the Log on Settings tab and ensure that the checkbox Always prompt for password is not checked.

Note: The configuration UI was discontinued by Microsoft and is not available anymore on OS Versions Windows 2012 or higher!

Server-side RDP settings using Group Policies:

The setting above can also be set and enforced by group policies. 

Windows 2003(R2):  https://technet.microsoft.com/en-us/library/cc786890(WS.10).aspx

Windows 2008: https://technet.microsoft.com/en-us/library/cc753697(WS.10).aspx

Windows 2008R2 or later: https://technet.microsoft.com/en-us/library/ee791928(WS.10).aspx

DontDisplayLastUserName is configured:

If your server is configured to not show the last user name, automatic logon may not work. See http://support.microsoft.com/kb/260711

To remove this setting on the Terminal Server: 

  1. Start Registry Editor (Regedt32.exe).
  2. Locate and click the following registry key:
    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
  3. Click the DontDisplayLastUserName value, and then click String on the Edit menu.
  4. Type 0 in the String Editor dialog box, and then click OK.
  5. Quit Registry Editor, and then restart the Terminal Server.

If you need a workaround and want the last user to not show up but still want to use automatic logon you can try the following:

The same key at:
HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System
clears up the login username's field with a normal user, but not RDP's fields. So RDP Auto-Logon should work.