Regedit:
HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon

New Key “Special Accounts”

HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon\Special Accounts

New Key “UserList”

HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon\Special Accounts\UserList

New DWORD (32bit) – enter name of the account.
Value of 0 = hide
Value of 1 = show

Source: Technet