Final response to this idiotic thread.

Steam MW2 is not connected to aIW.
I.E. if your friends have Steam MW2, and you have aIW you CAN NOTplay with them unless you get steam mw2, or they get aIW (which i do recommend)

IF YOU BOTH HAVE STEAM VERSION, just go and play them on that. If you want to host a private match with mods, have them download aIW!!