Wow! New Gates and Seinfeld episode.
This is all about scrambling any perception or stereotype you might have had about M$.
Update : It is, also, of course a kind of satire on / deconstruction of the Apple ads. With Seinfeld in the place of the "cool" (Mac) guy, and Gates as the boring, nerdy (PC) guy. Except in this case, the distinction is being shown as breaking down, both are equally weird, uncool, "bad" (flawed, selfish, stupid in the way all Seinfeld characters are).
The Apple / PC dichotomy that the Mac ads push? There is no such structure in the world. There's just the nihilistic despair of the human condition. A primal chaos from which a new M$ brand can emerge.