I don't think .mpg is a file extension that Windows Media Player can play. What I would do is download Windows Movie Maker, go to File, Import into Collections, import your video (combine clips if you have to), then go to File, Save Movie As and it will save it with a .wmv extension, which will play in Windows Media Player. Also make sure the movie is smaller than 2.1 MB, that's the limit for attachments on PT I know it's complicated, I'm sorry...it took me weeks to figure out how to do mine! Every computer and camera is a little different, so that may not exactly work for you, but Good Luck!