You can easily 'unwrap' MKV with MKVMerge. Providing the files that have been muxed to MKV are an avi with either an mp3 or ac3 audio track you will be good to go. In case the video and audio are separate simply remux them in
VDM (virtualdubmod).
MKVMerge is part of
MKVToolnix.
All software mentioned is free.
