Warcraft 3

So I got my warcraft 3 ROC cd key banned and a freind gave me a new one. Problem is I havent a clue now where my game is so I cant reinstall. I was wondering if there is a way to manually change my cd key from maybe the mpq (where its stored). I had even heard of ppl going into their registry and locating the war3 stuff and then somehow change their key. As you may be able to tell I have no idea what im talking about. Any info would be appreciated. Thanks in advance.