ISSUE: Missing image files in proper directory/format.
CAUSE: Indexing turned off on target drive (C:) !
After this problem, I had a further issue with another program; in resolving that I deleted it; that led to issues; long-story-short, I lost a dual boot system and now have a normal one OS boot system.
I then ran Ashampoo's WinOptimizer and in going through the modules discovered that NONE of my drives were set for indexing, only the default Windows files. Turning Indexing back on, rebooting and letting it idle a bit while the indexing kicked off, has resolved the issue. Now DS shows all the files in the folder.
I am assuming this may relate to the other issue I posted, that of sometimes getting the same image on all 3 monitors, even though set to differing images in DS.
I hope this helps if anyone else has the same problem.
..bigger mystery is how indexing got turned off in the first place...