Also, you have low level drive encryption which is actual drive encryption. Don't lose the passphrase. McAfee is an example. Or, Bitlocker aforementioned from Microsoft started with Vista I think.
Then you have file system encryption, aka NTFS file system encryption such as EFS and forward. EFS is not disk, that would be Bitlocker.
If you use Windows 7 ent, 8.1 pro use bitlocker. Part of the Windows.