Playing and editing DV-AVI files on a Mac

I have loads of video files thet I have transferred from MiniDV tapes and onto my computer. I used firewire cable and something called WinDV to transfer them, and as far as I know they are saved in the DV-AVI type 2 format. I copied the files onto an external hard drive for a friend, to edit on his Mac. But there is a problem. The files are there, but won't open on the Mac. They play fine on all my PCs. What do we do? Is this a file type incompatibility issue, or a software issue, or what? I was under the impression that the files on MiniDV tapes are natively DV-AVI (or is this wrong?), do you have to convert these to MOV or something while transferring if they are going to be used on a Mac? What do we do?