I recently bought crysis 2 from the flea market, I saw a game vendor was selling used games, one of them was crysis 2 for PC, im very new to pc gaming and have no idea what a (product code is). All i received was the disk and limited edition code. Apparently this code is in the game manual, But i didn't notice when i bought it the game manual wasn't in the case, i didn't know PC games came with one. What should i do, i cant play single player or multi player because it says i need to activate it. Is there a universal code or something? I cant take it back because the guy has left, and i cant sell it without a serial key can I? PLEASE HELP