If you need a standalone app to play MP4 files, why not use MPlayer? It's OpenSouce and cross-platform :) You can either use one of the existing front-ends (SMPlayer, MPUI, etc.) or you can easily create your own front-end. Also there is VLC Media Player as an alternative... Nevertheless you prefer Flashplayer, you could simply embed a HTML doc into your app (for exmaple via IE) and load the Flashplayer there. The HTML code could be generated dynamically by your app and load a local MP4 file for playback. Alternatively your app could only generate the required HTML code and then open the HTML doc with the default browser...