Change the Logon Screen Saver
Click Start , click Run , type regedt32 , and click OK .
Navigate to the following registry key:
HKEY_USERS\DEFAULT\Control Panel\Desktop
In the details pane (right-side), double-click the SCRNSAVE.EXE string value item.
In Value data , type the path and name of the screen saver, and then click OK .
IMPORTANT : Make sure that you specify the path correctly to the screen saver. If the screen saver is located in %SystemRoot%\System32, the explicit path is not required.
You have now changed the logon screen saver.