Since I skipped Vista, this may be an old question, I don't know.
In XP, the built-in SlideShow (Photos) screensaver would randomly rotate among images not just in the directory specified in the settings, but also in any sub-directories (and on down) of that directory. When I use the Photos screensaver in Win-7, it seems to use only images in the directory I specify, ignoring the rest of the tree below that.
Is there a way to get the XP behavior? Alternatively, is there some other public domain/open source Screen Saver with that or similar behavior that I can install?