Yes piracy is highly illegal, not to mention the method you are using is even more dodgy. You are downloading stuff from people assuming it's all "legit" and happily giving out your IP to anybody that wants to check.
Is it any wonder anti-piracy groups have realised that P2P users are easier to bust than the groups.
Now, with your problem it would be useful to actually know what is actually wrong. Is there an error message? Does it do nothing? Does it complain about your dodgy cd-key? I will tell you this though, most releases of this game are knackered and there are countless posts about it not working. Try looking at the comments on the torrent site - I guarantee you will see them.
Just buy the game (will be dirt cheap as it is relatively old in game terms), and use a No CD patch which I think are allowed by some if your DVD/CD drive isn't up to much.