I don't think you quite understand how the game ARMA 2 and DayZ work together. You must BUY WITH REAL MONEY both ARMA 2 and ARMA 2 Operation Arrowhead, both of them together are known as ARMA 2: Combined Operations. You cannot torrent one and buy the other, both MUST be bought in order to play online which is the only way you can play DayZ. Stop being cheap and support the company that makes such a good game. And yes buying the game just for DayZ is worth it, many have done it, you can look through all the awesome gameplay videos that are on Youtube, they aren't hard to find.