BitLocker is a new data protection feature available only to Enterprise and Ultimate editions of the Vista OS. When Bitlocker is activated, all files and folders in the selected volume will be automatically encrypted. Unfortunately, Bitlocker requires two conditions to work. You must ensure that a dedicated partition is set aside in your hard drive and your system must be equipped with either a Trusted Platform Module (TPM) 1.2 cryptography chip or a USB key containing the startup key. Probably the easier route would be to ensure that your system comes with a TPM chip, so be sure to check that with your retailer/manufacturer.
One very practical scenario for BitLocker is to safeguard your data from a notebook theft situation. Since this feature allows you to encrypt all your confidential data on another partition, even if you lose your notebook computer, no one else can access the data inside except yourself. Quite similar to Encryption File System (EFS)'s selective encryption, Bitlocker lets you encrypt the entire hard drive including Windows system files. This is unlike biometric scanners and the conventional user name/password logins, as Bitlocker renders the data on the notebook useless even if one extracts the hard drive and tries to access the data from another PC.