c0ltkiller

I recently bought Arma 2 Combined Operations off steam. I have ran both Arma 2 and Arrowhead. Then I tried to launch as Combined Operations and it didnt work. It still doesnt work and now I can't play DayZ(sole reason I bought Arma). Does anyone have any ideas on how I can get Combined Operations to work? Whenever I hit launch it opens a black command prompt and words come up real fast and then it self-closes. I have tried running Steam as an admin and I've verified the files. I'm out of ideas on what to do. Please help me.