Get extra codecs & also get a back up player just in case. I always recommend VLC as it has in-built codecs is & generally very reliable. See what it can do here http://www.videolan.org/vlc/features.html

For extra codecs & more, such as players, codec identifiers,etc. see CODECs list and alternate players for Movies (click on link)

You might also be interested in these tips:

1. Movie download issues

2. Learn to use Bitzi to see if there's any user feedback on the particular file: How to use Bitzi Web Lookup ...