Mounting a registry hive is one of those things that is extremely handy to know, especially when working with an offline operating system. To make it easier to understand I made this quick video tutorial to make the task less intimidating.  

This is a list of commands for the new Windows PE 3.0 based on Windows 7. There have been many changes to PE including the addition of a new application called DISM.exe or the Deployment Image Servicing and Management tool.