To encrypt the drive that Windows is installed on, your computer must have two partitions: a system partition (which contains the files needed to start your computer) and an operating system partition (which contains Windows). The operating system partition will be encrypted and the system partition will remain unencrypted so your computer can start.
In previous versions of Windows, you might have had to manually create these partitions. In this version of Windows, these partitions are created automatically. If your computer does not have a system partition, the BitLocker wizard will create one for you using 200 MB of available disk space. The system partition will not be assigned a drive letter and will not show up in the Computer folder.
Before you can turn on BitLocker Drive Encryption you need to make sure that your computer's hard disk has at least two volumes. If you create a new volume after you have already installed Windows, you will have to reinstall Windows before turning on BitLocker.
One volume is for the operating system drive (typically drive C) that BitLocker will encrypt, and one is for the active volume, which must remain unencrypted to start the computer. The size of the active volume must be at least 1.5 gigabytes (GB). Both partitions must be formatted with the NTFS file system. You can also encrypt data drives on the same computer, but the drive that Windows is installed on must also be encrypted with BitLocker.
The terms partition and volume are often used interchangeably. On most computers, they are the same: one partition equals one volume. On larger computer systems, however, it is possible to have a single volume span several partitions. BitLocker installs on a simple volume, where one volume equals one partition.
If you do not already have two partitions, you can use the BitLocker Drive Preparation Tool to help get your system ready for BitLocker by creating the required second partition.
If you are using Windows Vista Ultimate, you can download and install the BitLocker Drive Preparation Tool from Ultimate Extras. Download and install the Ultimate Extra called BitLocker and EFS enhancements. After you have installed this tool, type BitLocker into the Start menu search box, and then double-click BitLocker Drive Preparation Tool to run the tool. After the tool runs, you must restart your computer before turning on BitLocker.
If you are using Windows Vista Enterprise, you can get the BitLocker Drive Preparation Tool through these standard support channels:
Microsoft Volume Licensing Services
Microsoft Services Premier Support
For additional information about the BitLocker Drive Preparation Tool, see this Knowledge Base article on the Microsoft Help and Support website.
To install BitLocker Drive Encryption on a computer that does not have a TPM chip, go online to the Windows BitLocker Drive Encryption Step-by-Step Guide and follow the steps in Scenario 3.
If your computer meets these requirements, you can turn on BitLocker.
Open Bitlocker Drive Encryption by clicking the Start button , clicking Control Panel, clicking Security, and then clicking Bitlocker Drive Encryption.
If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
Click Turn on BitLocker.
Follow the instructions in the BitLocker Setup wizard.