Want to be able to view videos that are in .MKV format? It's simple really and the steps are short.

First off, you want Media Player Classic. That is the BEST codec EVER.
1. Download the K-Light Mega Codec Pack HERE.
2. Install it (it's pretty basic).
3. It may ask you to uninstall somethings. DO IT. Well, you don't have to, but it's recommended. Media Player Classic basically plays everything. The BSPlayer even comes with it, so uninstall that too if you have that on your computer.
4.Once it finishes downloading, open the video.
5. No subtitles? Don't fret just yet. Go to Navigate on the toolbar and go down to Subtitle Language. Select the English subtitle.

That's it! But wait! Is the list under Navigate empty (or not selectable) for you? There's still a solution for you.
1. Instead of going to Navigate, go to Play.
2. Go down to Filters.
3. Go to DirectVobSub.
4. Select the English subtitle!

There, you're done! It should be working now! .MKV is also used for dual-audio, that is, video that has two (or more) languages for you to listen to. Just select Audio instead.

Enjoy!