BitLocker serves two very important purposes: it provides both full-volume data encryption and a way to validate the integrity of early startup components before Windows Vista starts. Check out this TechNet Magazine article for an overview of how BitLocker works and how it can help IT professionals protect their organizations with full volume encryption, secure decommissioning, and more.

http://www.microsoft.com/technet/technetmag/issues/2007/06/BitLocker/default.aspx

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