Thanks to Cider, Mac users can run windows applications/games WITHOUT running a virtual OS. Now that I think about it… I'm not sure if this COD4 was actually made for mac or if it was a port running through cider. This works for many other things as well. The Codeweavers CrossOver also does the same type of thing using wine instead of cider. Somewhere on their site they have a compatibility list. I successfully use CrossOver to run Steam games like DOD:S and other stuff. With virtualization through Parallels or VMWare Fusion, you still need a copy of the windows OS. With cider/wine, you dont. Long Live Mac! The ONLY reason I ever used windows was because I wanted to play games.
Putty for Mac