Bitlocker is a full disk encryption feature that comes with the Windows 7 Ultimate and Enterprise edition. It is designed to protect user data by encrypting the entire volume with AES encryption algorithm in CBC mode with a 128 bit, combined with the Elephant diffuser for additional disk encryption specific security not provided by AES.
I shall walkthrough a simple setup for the Bitlocker using Windows 7 Enterprise.
First of all, go to the control panel and open up the Bitlocker.
The encryption should take some time and once the process is done, your disk is now secured.