i too have some files that i can't play in my Macbook Pro. My solution to that was to download vlc player.
Here's the link for it if you want to give it a try.
why cant I play avi files on my mac that are on an external storage device. The device was origanilly used with my hp pc. the files play fine on my lg tv with the internal media player it has and they aslo play fine thru the pc. do i need to reformat the files and if so i do i do this ?