I may be incorrect, but it seems the moderators waste even more time dealing with people who necro threads. I've been on boards where older threads are automatically locked. I don't see why you don't do that, or at least have a large blinking banner whenever you reply to an old thread warning of potential rule violation. But maybe this sort of thing has already been implemented. I haven't necro'd any threads lately.
For the pirated version prevention, the word detection method will probably help. An alternative might be a mandatory question during sign-up with a dropdown box: "Where did you acquire your copy of FF7?" [ebay, Craigslist, pawn shop, Salvation Army, used game store, a friend, The Pirate Bay, Rapidshare, Mega Upload, other download, etc.] Maybe have a box for "If other, please explain..."