The move away from Flash is ever so slow, but at least there is movement. Starting with Firefox 20 (due out in April 2013) Windows users will have support for H.264 videos via the Windows Media Foundation Playback. Also Firefox for Windows will be able to support AAC audio in MP4 and M4A files, and MP3 audio files without having to rely on third-party plug-ins such as Flash and QuickTime.
This feature is available, but not enabled on the current Windows Firefox Nightly Builds. Those currently using (can also get it here) the current Firefox 20 wishing to take advantage of this new feature need to enable via about:config tweak by setting media.windows-media-foundation.enabled to true.
Of course the other part of the move is to get developers to start using HTML5 formats in lieu of Flash, something that is not going to be easy given how long Flash has been the standard for media. Especially true for videos, though YouTube is moving closer and closer to HTML5 instead of Flash.
Source: Tom’s Hardware
Steps I fooled to get this working, not sure if all needed:
need Firefox 20+ and win vista+
set “media.windows-media-foundation.enabled” to true in about:config
Make sure you have Windows Media Center installed, follow this but turn on instead of off:
http://www.howtogeek.com/howto/15530/uninstall-disable-or-remove-windows-7-media-center/
Make sure you are not using the YouTube “HTML5 Trial”
(to set this I disabled flash then right clicked on blank video and selected “about html 5”)