Bolshevist, I went with the XP Home.... maybe I'll regret it later, but I honestly don't expect I'll be using any advanced features. I really just want to get a good (i.e. functional) gaming setup started without TOTALLY emptying my savings account.
Luckily there's plenty of kick ass games from the last two or three years I haven't played yet. They should keep me busy until I can save up enough for a half-life 2 worthy video card.
Of course this is all dependent upon my ability to actually put all this stuff together properly.... Should be an interesting weekend....