I'm not 100% sure if these steps will work if someone isn't logged on though!
To enable the screensaver, first
choose the screensaver you want. Look
in C:\WINDOWS\SYSTEM32 for files with
the .SCR extension - typically there
are the following (at least on my
Enterprise Installation)...
- SSTEXT3D - 3D Text
- BUBBLES.SCR - Bubbles
- MYSTIFY.SCR - Mystify
- PHOTOSCREENSAVER.SCR - Photos
- RIBBONS.SCR - Ribbons
One of the things to be aware of is
that you don't appear to have Direct3D
support at the logon screen so the
builtin screensavers above won't work.
Unless you have another file you might
want to grab the LOGON.SCR file from
an earlier operating system.
Once you have your screensaver (in my
case LOGON.SCR), open your registry
editor and navigate to the following
key -
HKEY_USERS \ .Default \ Control Panel \ Desktop

Below this key create the following
REG_SZ values...
SCRNSAVE.EXE = C:\WINDOWS\SYSTEM32\LOGON.SCR
ScreenSaveActive = 1
ScreenSaveIsSecure = 0
ScreenSaveTimeOut = 60 (or whatever timeout you want in seconds)
That's it - you'll have your
screensaver at the logon screen then.