If it won't play on your normal video player, make AVI Preview you default app. That way, it will open when you launch an avi file from LW. But AVI Preview probably only plays avi files right? Probably eventually you may need to sort out your video player. I suggested VLC b/c it plays most video formats (& some audio formats apparently) & it has codecs built into the program. VLC is not the prettiest of apps nor the most stable nor has the best controllers, but it works with a wide range of formats.