Images at startup and shutdown

Hi there, I have a Windows98 SE PC and the user that had it loaded somehow a background image that appears (tiles) when you startup and has it as the background for the login screen. Once we’ve logged in and you just go to desktop properties we’ve selected another image but that image is still there when you start up. Also when we go to shut down the PC instead of saying logging off or Windows is shutting… he’s put in another image somehow that is displaying briefly. How can we get rid of these images. Hope there’s someone that can help us.