Check out Video Inspector:http://www.kcsoftwares.com/index.php?vtb
After installing it, you can right-click a video and you'll have the option to open it with video inspector. Do so, and it'll check the codecs that the video uses against the ones that are installed. If it uses one you don't have, it'll tell you which one to download.
It sounds like you're probably OK on that count, but this will tell you for sure, and it's free.