I've just noticed an issue with some video files. This only appears to happen for .mp4 files, and not other video formats.
If you look below, the "Kung Fury Official Trailer" shows a thumbnail, and the Media Player Classic Icon. This is as I would expect.
The "Paperman" short video shows a thumbnail, and an icon for a folder, which isn't as expected.
From looking around, it seems that a program could have modified the registry, but I haven't installed or uninstalled anything (that I know of) to change it. How do I change the icons back?