Here I would  like to share the registry hack for Enable or Disable “Administrator” User account at the Startup screen in Windows XP.  Using this hack, you can also hide other user accounts from the login screen.  You just need to create a DWORD value for the user which you want to hide and set the default value as '0'. 

1. Launch Registry Editor. (Backup the registry before attempting to make any change).
2. Navigate to 
Accounts\UserList in the Registry Editor.
3. Create a New DWORD Value – Administrator
4. Double-click the Administrator key and change the value to 
            0 – Hides the user just from the welcome screen.

            1 – The user is shown at the Welcome screen.
5. Restart the computer for changes to take effect.