Hide Users from the Windows 7 or 2008 Welcome Screen

Open regedit
Go to HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon
Create new key  "SpecialAccounts" 

Create new key "UserList" inside  "SpecialAccounts" 

Create a new "DWORD 32 Bit Value" inside "UserList"  with the name of the user you want to hide

Set the value to 0