With Fx New Sound 4.0 you can replace the original audio of videos and movies with your own audio or narration done via a microphone. So, you can watch movies with a totally new audio track, or even put audio to silent films.
It works with AVI, MPEG, VCD, SVCD and DVD formats, letting you add to these videos the following audio formats: WAV, MP3, MP2 and OGG. You can even add photos(in GIF, JPG, BMP, TIF, etc formats) as independent photos to the videos.
To work correctly you need to have DirectX 8.0 or later previously installed. If you don´t have it, you can get it here:
Link.