Mac Gaming Mods

So should I return him the game and buy a new copy from a store? Or is there someway to make it work?

I have a PC and a Mac but at different houses. (1 at my mom's, 1 at my dad's) Here's my problem. I bought CoD2 for PC at a store (Gamestop). And at the end of my past school year I bought CoD2 for Mac from a friend for $20. I installed everything and SP plays fine, but when I try and play MP, I try ...