I sometimes have the same problem, could you tell me how you fixed it
Well the best thing to do is call or email the makers of COD2 and request a new cd key cause people are going around and collecting accessable cd keys and putting them into key generators for pirated games. I've had to do this already and it solved the problem. They may request a copy of your reciept, you name that your registered you game under if you did register which I honestly don't for I don't want all my info on the net. They will also ask for street address, phone number, city and state & zip code for US citizens, and where you purchased you product. A copy of your reciept will be the first thing they ask for its the most important thing, and always save reciepts for PC games no matter what. Good luck and hope this was helpfull cause once this happens it will happen again, TRUST ME.