Full Disk Encryption with BitLocker
Unlike EFS, BitLocker encrypts entire drives and better protects the drive's data from thieves. This full disk encryption tool was introduced in Windows Server 2008 and in the Enterprise and Ultimate editions of Windows Vista. Microsoft carried it over in the same premium editions of Windows 7 and added BitLocker To Go, which supports removable storage drives.
BitLocker primarily provides protection when the drive is shut down. It doesn't secure your data from attacks when you're using the computer. It protects your data if the drive is stolen, for example. However, you can also use EFS as discussed earlier to protect files when using the PC and to secure files from other users.
There are various requirements for using BitLocker's three different encryption techniques, creating several different configuration scenarios. If your computer doesn't have a Trusted Platform Module (TPM), for example, you'll have to insert a USB key to boot up your computer. To see exactly what methods your computer supports, refer to the BitLocker settings from the Control Panel.