Do you have a multiple Disk retail copy of Modern Warfare?
I have had problems in the past with multiple disks....
My usual solution is to copy all of the files from the disks into a folder on the desktop, then install from the folder.
Otherwise, I have found some success by going to:
1. PlayOnLinux Configure
2. Wine Tab
3. Wine Configuration
4. Drives Tab
5. check your D: drive and make sure it shows the drive mounted on your desktop
6. If not, remove drive and add a new one with the path to your mounted drive
You can right click the shortcut to the disk on the desktop to find where its mounted.
in Mint /media/username/diskname
I think...