Yeah I would go on Karma's point. The 74gb really isn't worth it, not to mention, 74gb will fill fast (I have a raptor 150gb, and I have to install some apps on a separate drive to leave room for games on it).
And with the motherboard, haven't had any i7 experience yet, but I have gotten some great life out of my gigabyte board.
And the operating system. Don't pay for xp, that would be silly. The windows 7 release candidate is solid, and runs on less resources than vista, and the license is good until next spring (the retail is slated for october release last I heard).