I suppose, you have downloaded the ISO image file of Call of Duty 4 setup. It is little difficult to solve your issue here. You have not mentioned any details about the kind of error you are getting. Let me tell you basics first, When you download Call of Duty 4 ISO files you need Power ISO to extract the file. Get the Power ISO from the official page of Power ISO and try to extract the set up you have downloaded. Remember the file where you have extracted the file, now go to that particular file. You'll find setup option there. Just click that and Call of Duty 4 will get installed on your system. You need a key for this game, I suppose you'd have got it with the set up and you can use that key.
Call of Duty 4 works well on Windows 7 so you should not face any issue related to OS. There are some specific requirements of Call of Duty 4, Before installing in it on your system make sure you system meets the specific requirements. Please be specific to the error or issue you're facing in the installation of Call of Duty 4, so that we can give solution for that issue or error.
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