Windows XP Startup/Shutdown Screens

I’m looking for a way to customize startup and shutdown screens similar to the old logo.sys, logoS.sys and logoW.sys on Win95/98 machines.
I used a Destkop Theme editor to do it, but that doesn’t seem to work anymore.
Does anyone know where these screens come from?
I have found the default logon screensaver, but absolutely nothing about splash screens for logon/logoff.