Lonk posted the following link in another thread and I wanted to put it here too.
http://forum.xda-developers.com/showthread.php?t=1801781
This link has some suggestions as to how to programmatically associate programs in Windows 8.x, ie FORCE IT by Deleting registy values.
1) change as needed: HKCU\Software\Microsoft\Windows\CurrentVersion\Exp lorer\FileExts\[extension here]\OpenWithList
2) remove all the keys beginning with 'AppX' for the desired file extensions in [HKEY_CLASSES_ROOT\[extension here]\OpenWithProgids]
