The final version of Vista SP1 focuses on under-the-hood improvements to reliability, security, and performance, with very few changes made to the interface or Vista's features.

Death of the kill switch

The change in Vista SP1 that has garnered the most publicity is the death of so-called Kill Switch (which Microsoft prefers to call "reduced functionality mode").

Currently (pre-SP1), if you don't activate a retail version of Vista after 30 days, or if you ignore a three-day grace period you're given after making so many hardware changes that Windows is no longer considered valid, your desktop turns black, the Start menu and desktop icons disappear, and you can only copy your data files, but you can't open them. In addition, after you use Internet Explorer for an hour, you're logged off.

In SP1, the Kill Switch in essence becomes a Nudge Switch. You'll be frequently reminded that you need to activate Windows, and the desktop background will turn black. Try to change it to another background, and an hour later Windows will turn it black again.

In addition, you won't be able to download signed drivers and optional updates via Windows Updates, although you'll still be able to get critical security updates. And you'll still be able to use Vista.

Why should you care about this if you've already validated your copy of Vista? The Kill Switch is part of Microsoft's Windows Genuine Advantage (WGA) validation system, and that system has caused nightmares for people and enterprises because of Microsoft glitches.

In August of 2007, many Vista and XP users found their Windows systems disabled by Microsoft because of a Microsoft WGA server glitch. The Kill Switch went into effect on many machines that had validated their version of Windows, and countless people no longer had access to their PCs. With SP1 and the death of the Kill Switch, that should no longer happen. That alone is reason enough to upgrade.

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See also:

Windows Vista: the definitive review

Windows Vista SP1 Release Candidate review

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