I have the Amazon version and I'm playing with these steps: 1- Install Arma 2 2- Update Arma 2 - (ARMA2 Patch 1.11) ON THE SAME DIRECTORY 3 - Install Arma 2 Operation Arrowhead 4 - Update Operation Arrowhead - (ARMA 2: Combined Operations / Operation Arrowhead / Reinforcements Patch 1.60) 5 - Run both 6- Install DayZ 7- Use this .exe to play as COMBINED OPERATION http://www.MegaShare.com/4269448 I download this exe from the original arma 2 forum and edited to launch the mod. Really hope it works for you guys.