For plenty of people, a big reason to upgrade to Vista SP1 will be the death of the dreaded “Kill Switch,” which in essence kills Windows if for some reason Microsoft determines your copy isn’t a validly bought version. Good move…but getting rid of the Kill Switch is something that Microsoft can easily do as an update without bundling into SP1. So why hold it hostage until SP1 ships? To force you to upgrade, and make the service pack’s uptake numbers look better.
Full Article – http://blogs.computerworld.com/microsoft_holds_end_of_the_kill_switch_hostage_to_vista_sp1