http://www.ebcvg.com/articles.php?id=670
Starting next Tuesday, April 12, computers running Microsoft Windows XP without Service Packet 2 installed will not be able to block the upgrade.
An announcement that appeared on Microsoft’s web site provides an explanation for the upcoming upgrade:
“Because of these significant improvements, Microsoft views Windows XP SP2 as an essential security update and is therefore distributing it as a "critical update" via Windows Update (WU) and the Automatic Updates (AU) delivery mechanism in Windows. Microsoft strongly urges customers with Windows XP and Windows XP Service Pack 1-based systems to update to Windows XP SP2 as soon as possible.”
So ready or not, on Tuesday, “un-patched” boxes will have SP2 downloaded to their networks and computers, but, what happens after that?