Ok I'm running Windows 7, 5.1 Surround using analogue connections (Media center already hates me and will only allow me to set it as 2.1), however this is not the issue...
When playing some HD .mkv files, the video will play but not sound. This only happens for SOME .mkv files. The files all work find in wmp, vlc, the usual media players, but I want them working in media center!
I've tried various codecs and stuff, but not one has affected media center at all.
This might be a stupid question but did you check to make sure the correct audio track/device was selected? When I open some .MKV's in VLC they might default the audio device to 5.1 and when I'm listening through my 2.1 desktop speakers it won't produce sound.
Hopefully its a simple fix like this one. If not, maybe the encoding for the audio isn't supported, such as AC3 or DTS. Make sure you have codecs that support those audio types if you don't already.
also my media center doesn't like the fact my unit is 7.1 surround so I had to buy a second set of speakers and connect them directly to my tv tuner card.
i gave up trying to reconfigure, wasn't working.
i did not try and update drivers or anything like that, all I tried was to reconfigure in media center set-up..