Windows Vista includes a new hard drive encryption feature called BitLocker Drive Encryption. BitLocker can be a very useful security feature for businesses and home users that have sensitive and confidential information stored on their computer. Unfortunately, BitLocker Drive Encryption by default requires a Trusted Platform Module (TPM Chip) version 1.2 or later installed in your computer. A lot of the computers and laptops on the market do not come with TPM chips installed since they are typically only found in premium model business computers. If you have Windows Vista Business, Ultimate or Enterprise but do not have a TPM chip, you can still use BitLocker Drive Encryption.
Press the Windows button, type gpedit.msc and press Enter.
Navigate through: Computer Policy → Administrative Templates → Windows Components → BitLocker Drive Encryption.
Right click on Control Panel Setup: Enable advanced startup options and select Properties.
Check Enabled and click OK.