Yeah, you are missing codecs. So you can either install Perian to support several codecs in Quicktime, or install VLC (videolan), a video player that can natively play most video formats. I only use VLC as it plays almost anything, does subtitles perfectly well, it's fast and it should suit al your needs. Installing Perian makes me feel like a windows user, who has to install codecs and drivers to get stuff working The good thing with Perian though, is that it also allows you to play DivX videos in Frontrow (as Frontrow uses Quicktime). So if you're setting up a Media Center and you would like to use Frontrow as media sotware on it, Perian would be your best choice.