How is this technically (not legally) possible? (Score 1)

How exactly might Microsoft go about shutting-down a copy of XP if it *doesn't* have WGA installed, and if it *doesn't* connect with microsoft servers (presumably to allow the "kill code" to be sent remotely)? Are we thinking that the original code for XP contained this "kill date" all this time? Or did some other, earlier, update (e.g. SP2) include instructions to self-disable the installation this fall, barring further instructions from the mothership? Forgive any naïveté, but I don't understand how *not* having a piece of software installed can cause XP to shut itself down, unless it was designed to do so from the start, which seems (to put it lightly) unlikely.