I started this thread and after repeated disastrous Windows 8.1 updates reinstalled the dreaded KB2975719 and another KB file back onto my computer, which caused IE to crash when trying to view iPhone movies. Me personally, I'm moving to a Mac when I next replace my computer..
After much Googling, my brother, an IT Manager, identified TWO updates causing the problem with iPhones videos.
REMOVE both KB2975719 AND KB2995388. Switch OFF automatic updates and manually download security updates as and when required.
I now have no problems at all viewing files.
To remove the files, go into Control Panel and there's an icon which, off the top of my head, is Windows Update.
If you need help finding the files, reply to this thread and...