BitLocker is an operating system-level extension to Vista and Windows 7 that combines on-disk encryption and special key management techniques. The data and the operating system installation are both protected by two-factor authentication, specifically, a hardware key used in conjunction with a long passphrase.
Windows 7 ultimate includes BitLocker To Go, which takes the capability of BitLocker that performs bit-level full volume encryption and extends its use to removable storage devices such as USB keys, meaning if we lose our USB thumb drive, our data is safe