Check the file with Bitzi before download...if it's not out in DVD yet (still in cinemas here & not out on DVD until March) then you might have downloaded a misnamed/junk file
How to use Bitzi

If the file is genuine, check the thread below for links to codec packs & VLC player (free) which has codecs installed to play most file types.
CODECs list for Movies /Alternate players / Video help forums

Make sure to scan all files that you download with your updated AV, before opening them.