I bought Call of Duty: Modern Warfare for the xBox. Before that I had played Warzone. Now when I insert the CD and start CoD, it says "not bought" for multiplayer.
How do I install it?
Uninstall Warzone and then completely install Modern Warfare. Now would be my first thought.
I think I solved it, you can download the individual packages in the store - let's see if it should work.