I got this game from a friend and so i install it on my laptop. After playing the first 3 missions, it tells me to enter in my product key. I look on the manual and type it in but no luck. It says that It's been used too many times. I asked my friend for help but he said he got it from his friend. I don't mean to be a freeloader off of the people who did buy this game but may I just ask if you could share product keys? I wanted to see if the single player was good.