Navigate to Black Ops 2, click on SETUP and then select your Black Ops 2 game folder.
The folder you need to select is most likely called Call of Duty Black Ops II and should be in Drive letter\Program Files (x86)\Steam\steamapps\common.
In both cases, the way to fix this issue is to click on Game settings in the launcher and to select the folder that contains the Black Ops II files.
If you can't find it then read the guide from the start again.
Navigate to Modern Warfare 3, click on SETUP and then select your Modern Warfare 3 game folder.
The folder you need to select will be called Call of Duty Modern Warfare 3.
Do not select your Games folder or your Document folders. Select the folder with Modern Warfare 3 files in it!
In both cases, the way to fix this issue is to click on Game settings in the launcher and to select the folder that contains the Modern Warfare 3 files.
If you can't find it then read the guide from the start again.
Navigate to World At War, click on SETUP and then select your World At War game folder.
The folder you need to select is most likely called Call of Duty World At War and should be in C:\Program Files (x86)\Steam\steamapps\common.
In both cases, the way to fix this issue is to click on Game settings in the launcher and to select the folder that contains the World at War files.
If you can't find it then read the guide from the start again.
Navigate to Black Ops, click on SETUP and then select your Black Ops game folder.
The folder you need to select is most likely called Call of Duty Black Ops and should be in C:\Program Files (x86)\Steam\steamapps\common.
In both cases, the way to fix this issue is to click on Game settings in the launcher and to select the folder that contains the Black Ops files.
If you can't find it then read the guide from the start again.