OK I think I see what you're asking for. The value you want to change
is in the same registry folder ("HKU\Default\Control Panel\Desktop")
as the webpage indicated in my answer above, it's called scrnsave.exe.
Put your replacement for login.scr in ...\System32, update the
registry value as necessary.
Cheers,
Chuck
Paranoia comes from experience - and is not necessarily a bad thing.