Sometimes you will receive an audio or video file type that your audio player (Express Scribe, FTR, Transcription Buddy, Start Stop, etc.) will not play. In those cases you may need to convert the files to a different file type.
Some programs you can use for this are:
Switch (by the makers of Express Scribe - there is a free version and a Plus version) - http://www.nch.com.au/switch/