Problems importing movies?

I'm trying to import movies onto iTunes, but nothing happens when I do. I'm trying to import an .MPEG-4 movie. I tried dragging and dropping the videos onto the list, but it didn't work. I tried importing it, and it didn't work either. I tried the similar thing with a .mov file, and it showed up, as well as a .m4v file. Does iTunes 7.5 just not work with .MPEG-4 files?