Winamp no doubt is one of the most used music players but unfortunately it doesn’t play some file formats like .MKV, .MP4, .RMVB, and .MOV. Here’s a tutorial to make WInamp play such files. Here’s how you do it:
First of all you need to make sure you have installed most of the necessary codec files. If you aren’t sure about it then I advise you to install the K-Lite Codec Pack. Also download and install QuickTime Alternative for playing quicktime videos.

Now start Winamp and go to Preferences> Plug-ins > Input and Select Nullsoft DirectShow Decoder in the right hand side and click “Configure” below.

By default, the DirectShow configuration for Winamp should look like above.

Extend the list by adding “;MP4;MKV;MOV;RMVB” (without the quotes). This option enables Winamp to play .MKV, .MP4, .RMVB and .MOV files using DirectShow filters. Once done click ‘OK’
That’s it, you should be able to play MKV, .MP4, .RMVB, .MOV Files in your favorite Winamp.
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I am able to play my MKV files in winamp thanks to your post here. But I am unable to activate subtitles in winamp. In VLC media player I can right click the image and a subtitles option is in the menu. I went into the Video formating for the Direct show on Winamp using Alt+3 and found the key bindings. It says to use ‘S’ to toggle the subtitles but that isn’t working for me. Do you have any suggestions?