I told you already get a different player. Try GOM. Its free plays almost anything and pretty nice interface. Oh and side not .mkv is a gay *** format. Even when you get it to play it doesn't play as well especially with subtitled shows. Play back is horrible no matter what players and/or codecs you use unless the people who encoded it did a really good job. At least in my experience
Well then you just fail. And/or missing some basic codecs. Hell just hit the find whatever button that almsot always pops up when it fails to play something