Vista Desktop image won't stay sized

I've got a new wide-screen monitor and video card, All in Wonder Radeon
running with Vista Ultimate. I've gone to Personalize, Desktop Background
repeatedly and clicked either the button on Fit to Screen or Fit to Screen
with Crop. That selection will stick until the grahic is changed when it
reverts to a partial screen. Occasionally it will revert to Tile.

I'm using images that are 9x16 aspect from Webshots.

Is there some way I can lock the desktop image in whatever aspect I've
selected?
Thanks for any assistance you might offer,
TerryS