BIG trouble with video.

So, I had thought video would be easy, and of course, I can't even load the videos on my computer. So, it seems I will not have a movie posted to my blog today. My movies loaded into my computer as MPEG files, and for some reason imovie won't take that format, but I can't seem to even start to convert the MPEG files into anything else. The problem is similar to one I had with audio, but even my Switch program won't allow me to convert the files. I've pretty hit a wall for now...