Tying a hard drive to a Trusted Platform Module (TPM) through the use of PKI and encryption keys is an incredibly effective methodology for protecting the operating system drive. Microsoft introduced support for Bitlocker with Windows Vista and both continues and expands that support in Windows Server 2008. I have been getting lots of questions about bitlocker and how to set it up etc. I decided I would make a short video about the process both with and without a TPM.
The TechNet Bitlocker FAQ's also address many of the common questions I am hearing.
Last but not least it would be pertinent to know that Bitlocker is not the ultimate security solution in the universe. (Princeton University claims it can be breached with a recovery of the key if it is resident in DRAM) It does represent a great tool in your security toolbox. The principles of Defense in depth still apply; use Bitlocker to add a little more depth to your security.