I bought Arma 2 when it first came out, and have had it installed ever since. I just bought Operation Arrowhead and installed it ( for z Day:3) with Steam but the two didn't combine. I can't play them in a single game, it only lets me play Arma 2 or Arrowhead separately. What do I need to move to change to make it work?
My Arma2 is boxed retail, and my Arrowhead is a steam digital copy.