How can Windows Vista help protect the data on my Trust Laptops if lost or stolen?

Windows Vista has a feature called Bitlocker Drive Encryption. With Bitlocker the entire Windows volume is encrypted to help prevent unauthorised users from trying to break Windows file and system protections. The data on the disk is even secure if the disk is removed and attached to a different device.
The encryption key can be stored on the preferred Trusted Platform Module (TPM) chip if the laptop has one, or the key can be stored on a USB flash drive. Storing the key on a USB flash drive would require the user to insert the key each time before the laptop can be used. Administrators can manage the backup and retrieval of encryption keys through Active Directory.

Further information can be found at:
http://www.microsoft.com/technet/windowsvista/security/protect_sensitive_data.mspx