Get into the your computer registry (via regedit) and search for "Digital Distribution" which should be located in HKLM\Software\Activision\Call Of Duty 4 (x64 HKLM/Software/Wow6432Node\Activision \Call of Duty 4)
and change it to "Not Digital Distribution" and then run the downloaded patch installer.
After the install finished then changedthe "Not Digital Distribution" back
Thank meanman, not me.