I've used Livestream for every stream I have ever done, but it doesn't do games all that well. Is there any (free) software that would help me record games, in HD? I'm thinking of doing Let's Plays, but I don't really know where to start.

If anyone could give me some information on it, and perhaps walk me through some steps if it's not just a 'plug in and play' thing, I would be very grateful.