quit trying to convert and go get a player (non-WMP) that plays mp4s. When you convert there are much more to do in good converting that just a one click converter that goes from mp4 to mpg. There are codecs and other things involved that you may not have which is also why you dont hear audio. There is an app called
Gspot that you can run for a audio/video file and tell you what codecs it needs to play and if you have them or not.