Downloaded those and reinstalled. Still crashing. My friend found the solution " I had to copy the ArmA 2 Free folder into Operation Arrowhead folder. I renamed that folder arma2free. Then i had to modify the launch option so that when i start OP, it launches arma 2 free as a mod as well. like this : -mod=@dayz -nosplash -noautoupdate -mod=arma2free;expansion;ca"