Have more faith in humanity Tommy, but I'm glad I could help you both (and myself in the process)

Guys, as I said, try to install older 4.0.X release first (uninstall the one you have now ofc). It helped me, might as well help you.

Nope, not portable. I tried installing it many times to the same effect.

Ha! Update on the subject at hand. Instead of further messing with registry, i've decided to find the oldest MM4 release, which was 4.0.1.1461. Uninstalled the 4.0.3 one, installed the oldie, and *ta-dam* it works. MM is now listed under Default Programs, it assotiates the files via Options no ...

I have the exact same problem and slowly, but surely it's driving me mad. When I go to OS Integration all the audio files are selected, as is the "Re-associate file types" option. Also, some of the video files are selected, so I deselect them, reselect the audio files and nothing happens. Tried ...