Your friend said it is a great movie but the damn thing won´t play in your computer. The screen remains black and you hear no audio at all. Many users tend to download a huge codec package and install it on their system. Sure, the movie most likely plays fine after this method but it seems a bit like an overkill if installing one single codec would have lead to the same result.
MediaInfo scans a video or audio file and displays its technical and tag information. Information include general information like title, author and duration but also relevant information about the audio and video codec used to create the file. The freeware provides a link to a player who is playing that file and a link to the codec if you already have a favorite player.
The supported formats list is to large to be listed here at ghacks, take a look at the MediaInfo supported formats list for a complete listing. A similar tool is Gspot which offers basically the same functionality and is freeware as well.
Both tools offer in depth information about the analysed file which help if you encounter other problems, for example bitrate related problems.

Find out which audio or video codec is missing
Video Inspector Displays Video Codecs Information
Check for and add missing Video Codecs
Video To Audio With Audio Extractor
Avicodec is another alternative:
http://avicodec.duby.info/