When the Log on to Windows dialog box appears, you can control whether the Domain box and Log on using dial-up Connection appear. This can be toggled by the Options button, which alternately displays and hides them.
To control the initial display, use Regedt32 to navigate to:
Double-click the ShowLogonOptions value name in the right-hand pane. This REG_DWORD data type can be set to:
0 - to hide the options when the dialog opens.
1 - to display the options when the dialog opens. This is the default.