If you are looking for an open source video player, this link may be of interest:
http://www.getmiro.com/
It will play Windows Media, Quicktime, MPEG 1, 2, 4, H264, AVI, DivX, XviD, Flash, OGM, and lots more.
With trakAxMobile, you can save your audio & videos as MPEG4, WMV, .3GP, AAC etc., so this is a neat little player to playback your mobile videos on your PC.
