Instructions
Turn on your PS3 console and a controller and scroll over to the ̶0;Game̶1; menu. Select the ̶0;Game Data Utility̶1; from the drop-down menu and scroll down to the ̶0;Call of Duty 4: Modern Warfare̶1; list item.
Navigate to the ̶0;Updates̶1; section of the page and then scroll to ̶0;Game Update 1.40.̶1; In some PS3 systems all game updates are combined into one file, so if this is the case select the ̶0;Game Update̶1; file.
Click on the ̶0;Delete̶1; option in the "File Details" page that opens up and then confirm the operation.
Load the ̶0;Call of Duty 4: Modern Warfare̶1; game disc in your PS3. Update 1.40 will now be bypassed and the original, non-updated game will start up.