What a major mess up.
Plenty of people are reporting that Black Ops 2 disc 2 on the PC is actually a Mass Effect 2 disc, and somehow there has been a major mess up at a manufacturer plant where discs are pressed.
There are a bunch of logical explanations as to how this happened but such a thing is quite rare and hasn’t happened before, or at least hasn’t been reported properly.
Mass Effect 2 is an old game by now, so how did that end up on Disc 2 of the PC version of Black Ops 2? If you have the game on Steam, you can just download it via Steam servers after inputting your activation key. There is a workaround available, so no need to panic.
It seems Activision could recall these copies if this issue blows up and you know it will. Check out the video below that shows a user struggling with the installation.