FinalMugetsuHD

I purchased Arma 2 Combined Operations 4 days ago and I still cant play this mod, I tried everything! I searched on google youtube dayz wiki..nothing I always get errors while trying to join a server, I deleted and installed the game now for like 15 times and now I cant even start Operation Arrowhead because it says bad serial number giving in setup, I mean seriously WTF? I should have bought a better game with the money... Anyone has WORKING guide that helps me installing DayZ and get rid of the error when im trying to launch OA? What I tried: Installing the mod manually Six launcher DayZ Commander Worrom Any other ways to install it? I watched like 10 videos on youtube and did the exact same thing that they did but I still get errors