Codec Guide

The K-Lite Codec Pack contains a tool called MediaInfo Lite. With that you can get a lot of useful information about a media file. For example what kind of audio and video format it contains.

If you haven't got the K-Lite Codec Pack installed, then you can get the tool here:
http://www.codecguide.com/download_other.htm#mediainfo

If you are having problems with a specific file, then it is helpful for us if you include the output of MediaInfo in your topic.