Teerex! Worked like a charm. Thank you for the tip
I make use of my Macrium Reflect software quite often, heh. So I actually restored to an image without any catalysts installed to start with absolute clean slate. Installed IE10(I unhid the platform update, but I notice this time it didn't automatically install with IE10 like before, and it vanished from optional list after install of IE10 and did not appear in update history?) Anyway and then did FULL 13.10 catalyst install again just to verify problem. Still same problem. So I went back to clean image and did your custom install suggestion. I unchecked:
AMD APP SDK Runtime
AMD Accelerated Video Transcoder
AMD Drag and Drop Transcoder
AMD Media Foundation Transcoder
Now WMP plays avi files again.