To protect sensitive data on your PC, encryption methods always helpful.
BitLocker Drive Encryption is security feature in the Windows Vista operating system that provides protection for the operating system on your computer and data stored on the operating system volume.
BitLocker ensures that data stored on a computer running Windows Vista remains encrypted even if the computer is tampered with when the operating system is not running.
I searched on net to find how to configure it & found a good article. Links are as follows.