My advertised copy of XP Pro has been registered, and receives regular updates. I still wouldn't use it for anything but learning, and intend to bite the bullet and get a copy of it from Staples for $299. It's mine then and hopefully will not be bulked by some new rule that comes in at the whim of MS. at some arbitary date.
As mentioned on the adblocker thread, my pal in the uk is aware or the real figures for Visa take up (sic) and mentioned extended support time to 2010 or some such date for XP.