what the heck is a mkv file?

Its an odd video file, but can i convert it to avi? and keep subtitles ?

I just recently got something that was .mkv. I can't remember what. I had to look it up myself. Basically it's like a compressed video with its own filetype. Like if someone saves something as .divx or whatever. Its a DivX compressed file. Though those are usually still kept as .avi, just using the compression. Anyway, I got something called Lazy Man's MKV. Which seems to have VobSub, which I know puts up subtitles in videos if the subtitles are seperate. So this makes me think it was my FF7:AC that was the MKV file. Anyway. There's my rundown. I'm sure some techie will break it down better for you

Matroska. It's a video container format. If you install the video codec pack linked to from cl_out's sig, it should have the mkv codec that Vyk referred to.

If you are looking for a utility that specifically converts mkv to other formats, check out: http://www.videohelp.com/tools?tool=AVIMux_GUI