For Windows 7 first RSAT (Remote Server Administration Tools for Windows 7 with SP1) should be installed and after that from Turn WindowsFeatures on or off »BitLocker Recovery Password Viewer« can be installed.
For Windows Server 2008 R2 it is
in »Add
Features«, »Remote Server Administration Tools«,
»Feature Administration Tools«, »BitLocker Diver Encryption
Administration Utilities« and select »BitLocker Recovery Password Viewer«.