Hide user accounts from the Windows XP Welcome Screen
If you want to hide a particular user account from the Welcome Screen in Windows XP, you need to create a special value in the registry for each user and set the hide/show value to 0=hide, 1=show under the following key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList
Under this key, create a new DWORD value which HAS TO MATCH THE USERNAME EXACTLY and set the value to either 0=hide or 1=show. Repeat for each user.