Note: This should work on any game which uses an MSI file.
First make sure the game you are having problems with is uninstalled!
Then Delete the folder where you were trying to install too.
Download the ‘Windows Installer Clean Up’ program from
HERE and install it.
Once installed, if the program doesn’t start automatically then start it from the Start Menu\Programs menu.
When the program starts it will run through your system and list most/all programs installed.
Find the offending game (For example find Call of Duty 4 in the list)
Highlight the game and Click ‘Remove’.
Exit the program and now you will be able to install your game from your converted DVDs.
The installer will now recognize DVD2.