On my PC, I downloaded VLC, and these files play fine - I have never downloaded an XviD or DivX codec on this computer.
On the Mac, the files didn't play in Quicktime. We downloaded VLC, and they still didn't play. rwrylsin followed instructions we found on getting XviD working which involved downloading the DivX codec and some other thing which runs XviD through DivX (?? I may be misremembering/misunderstanding), but they still don't play. Help ? Surely this sort of thing should Just Work[tm] ?