Thus far we covered the steps necessary to capture a system image with Hyper-V installed, and how to install Windows and Hyper-V at the same time without dealing with system images at all.
Let's take a step back and talk about system images again. Images are a great way to deploy a customized version of Windows to many different workstations or servers without having to go through the effort of configuring each system independently of each other.
Even if you're just setting Windows Vista or Windows Server 2008 up from a DVD, you're still using an image to do the installation. If you look on the DVD in the \sources folder, you'll find a file called install.wim. WIM stands for Windows IMage, and it's an actual image of a real Windows installation that Setup applies directly to your hard drive (and then manipulates a bit, but that's a different story).
The cool thing about WIMs (and there are actually many, but I'm just going to stick with the one that's relevant to this post) is that - using imagex.exe - you can mount a WIM as a folder on your Win6 (that's Vista and Server 2008)-based system and copy files to or from it, then save your changes.
So what does this have to do with Hyper-V installation?
Well, hang on... there's more that we need to talk about.
With Windows Vista and Windows Server 2008, some really cool work was done to make the operating systems more servicable. I'm not really in a position to go into all the details, but one of the absolute coolest side effects was the ability to service a Windows installation without actually booting it, which is called Offline Servicing.
Hyper-V, Hypervisior, Windows Server 2008, How To, Guide, Knowledgebase