In Windows 2000 and Windows Server 2003, if a user omits the domain name when using a dial-up or VPN connection, Routing and Remote Access and IAS try to authenticate user accounts against the domain that the server belongs to.
To change the default domain:
1. Use Regedit.exe to Connect Network Registry on the File menu.
2. Type the computer name of the RRAS or IAS server into the Enter the object name to select (examples) box, and press OK.
3. Expand the server's HKEY_LOCAL_MACHINE hive and navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RASMAN\PPP\ControlProtocols\BuiltIn.
3. Double-click, or add the DefaultDomain Value Name, a string (REG_SZ) data type, and set the data value to the domain name you wish to use.
4. Press OK.
NOTE: To authenticate against the server's SAM, type the server's computer name instead of the domain name.
