With Windows Vista Ultimate you can download an Ultimate Extra, the Bitlocker Disk Preparation Tool (BDEHDCFG), which is very handsome. However, as an Enterprise customer - for Windows Vista Enterprise Edition, you can request the tool also through Premier Support or Customer Support:

 http://support.microsoft.com/kb/930063

To encrypt drives and to verify boot integrity, BitLocker requires at least two partitions. These two partitions make up a split-load configuration. A split-load configuration separates the main operating system partition from the active system partition from which the computer starts.

The BitLocker Drive Preparation Tool automates the following processes to make the computer ready for BitLocker:

Creating the second volume that BitLocker requires
Migrating the boot files to the new volume
Making the volume an active volume
When the tool finishes, you must restart the computer to change the system volume to the newly created volume. After you restart the computer, the drive will be configured correctly for BitLocker. You may also have to initialize the Trusted Platform Module (TPM) before you turn BitLocker on.

Urs