BitLocker is intended to prevent the theft of data on computers that have either been lost, stolen, or prematurely/improperly discarded. This new security feature is available from Microsoft on the following operating systems: Windows Vista Enterprise and Ultimate, as well as Windows Server Longhorn.
BitLocker utilizes a feature known as a Trusted Platform Module (TPM) to protect system data and ensures that the system was not tampered with while it was offline. It prevents malicious attackers from successfully running hacker tools in an attempt to either break the system’s file protections or perform offline viewing of data on an unprotected drive.
The two main tasks performed by BitLocker to achieve data protection is full encryption of the hard drive and checking the integrity of boot component upon startup. Drive encryption prevents unauthorized users from access the data stored on the drive, and the integrity checking validates that the protected hard drive is still in the original computer, and ensures that decryption is allowed only if the system appears not to have been tampered with.
BitLocker is a completely integrated part of the Windows Vista operating system , and even includes its own Recovery Console in the event that data needs to be retreived off a failing or failed hard drive.
In addition to the features mentioned above, BitLocker also offers the ability to lock the normal boot process. The boot process is actually interrupted, and the user is prompted to enter a PIN number, which must be entered correctly for the system to boot into the operating system. Bootup can also be protected via an external USB key that contains a security key which BitLocker validates against while booting the system.
The use of BitLocker is transparent during day-to-day use, and is configured via its own wizard, and can be further configured via a Windows Managment Interface (WMI).

