Hey, I noticed that after the Firefox 42 update (or maybe sometime before this) my H264 support was gone. The test site http://www.quirksmode.org/html5/tests/video.html shows only "No video with supported format and MIME type found" message for the H264 movie. The other two work fine. The youtube test site also tells me that H264 is not supported. I then found that the Windows N version i am using is missing the Media Feature Pack and that firefox requires that for media playback, so I installed it. After restarting the computer firefox crashed when starting it again and again. I had to reset it. No I am back to square one. Firefox is runnning again but H264 is still not working. I am thankful for any suggestions.