Slideshow Screensaver in Vista before logon?

Hi,
In XP, I was able to run the slideshow screensaver (ssmypics.scr)
before logon by specifying it in HKEY_USERS\.DEFAULT\Control Panel
\Desktop\SCRNSAVE.EXE. When I try to do the same in Vista, I
experience an issue where I am unable to specify the parameters of the
screen saver in the registry.
Notably, XP has a Screen Saver.Slidshow Key in .DEFAULT where the
parameter values are stored. These folders are missing in the Vista
registry.
The default behavior is a blank screen, and if I try to manually
create a DWORD with the FolderPath value, I receive a message in the
screensaver that an error is preventing the slideshow from playing.
Can someone please help me determine where to specify the parameter
values to make this work?
Thanks,
Jamie

Hi again,
Just one detail to be clear: I am using the new Vista slideshow
screensaver: Photoscreensaver.scr.
Thanks,
Jamie