Hello Just a person who might have had the same issue as you
why don't first go to REGEDIT on RUN and look for the activision software in HKEY_LOCAL_MAHCINE and look for the call of duty 4 folder. Then, click on the UninstallString key and just press ok without changing anything. Then, free up some space in your hard disk where the COD is installed and try to uninstall again. Just worked for me, hope it works.