If it is mpeg-2 you probably need to download/install a
codec(oder) first, e.g. Elecard's can be downloaded
here.
There are some simple and free utilities for you to find out what kind of movie-file you're dealing with. Try e.g. Avicodec or GSpot. You find links to the downloadsites under item 2 of my
Help to Help-post (click on link hereunder).