1 ) Download and install Monogram GraphStudio (->google, it's freeware). Also, install Haali Media Splitter if you don't already have it.
2 ) Open GraphStudio, go to Graph -> Insert Filter.
3 ) Select Haali Media Splitter and select the file you wish to convert. (let's say "movie.mkv")
4 ) Select Haali Matroska Muxer and type the filename you want the movie to have ("movie.mp4")
5 ) Connect the pins for Video, Audio and Subtitle from the Media Splitter to the Matroska Muxer.
6 ) Right-click on the Matroska Muxer, select Properties -> Options -> Output -> File Type, change Matroska to MP4.
7 ) [Optional] Name the video, audio and subtitle tracks
8 ) Hit OK, then press the green Play button.
9 ) Wait.
10) ? ? ? ? ?
11) PROFIT
