User Disapeared at Log on Screen

1. Select Run from start menu or "Win logo+R"
2. Type: control userpasswords2
3. Click OK
4. In the box that appears, there should be a check box that says "Users must enter a user name and password to use this computer."  If this box is not checked off, you can check it off and then save your changes by clicking the "OK" button.

You can Also try the following:

1.  try holding down the Shift key on your keyboard when your computer is booting up to force the login screen to appear. **But this is temporary and will only work for that single logon.

     2.   try typing in the Run box the following command: rundll32 netplwiz.dll,ClearAutoLogon