Kurt Shintaku's Blog

Organizations that use AU to keep their computers up-to-date can use a free Blocker Toolkit to block automatic delivery of IE7. This blocker has no expiration date; you can find more information in the blocker FAQ. I also recommend you review the additional information for IT administrators at the Windows Update/Microsoft Update site on TechNet. Organizations that want to block the distribution of IE7 through AU should have their blocking measures in place by TODAY, November 1, 2006.

http://blogs.msdn.com/ie/archive/2006/10/19/be-ready-for-automatic-update-distribution-of-ie7-by-november-1.aspx