This tech-recipe describes how to edit the registry to prevent XP from displaying the last user who was logged on.
1. Start the registry editor (regedit.exe).
2. Navigate to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system registry subkey.
3. Double-click the “dontdisplaylastusername” value (or create the DWORD type value if it does not exist).
4. Set the value to 1 to enable the feature or 0 to disable it.
5. Click OK, and close the registry editor.