Unless you are only doing one or two virtual machines with Windows Server 2008 R2 in Hyper V, or any virtualization software or Windows OS for that mater, you will want to save yourself some configuration time by creating an image of the OS you will be using. Windows gives us a very easy utility to do this called sysprep. It is found in the Windows directory on your system drive under System32\sysprep.
Since I do a lot of work with SharePoint and all of its related systems, I create several images so that I can quickly create a server based on what I need at the time. First I create a "base" server image. This is the generic install of Windows, no Roles installed. This gives me an image that I can use for any custom purpose. One thing that you MUST do first is to run Windows Update. You do not want to waste time on each VM getting it up to date. Do this first, then use sysprep to create your image.
After making an image of this disk, I will use the image to create a new server and then add the specific roles that will make it in to a generic image of the server and role that I want to have on hand. I always create an image of a server with IIS, and the latest versions of the .NET framework.
For technical reference, Microsoft has a page for the command line options. You could use the UI, but... I don't trust it. The line that I use is the following:
sysprep /oobe /generalize /quiet /shutdown
This removes all of the security information that is created when the server is first installed, and will put the server state in to the welcome mode to prompt you for information when you start up the server the first time.
From here copy the .vhd file somewhere safe. This is the generic disk master that you will create all of your new VM with. Be sure to name the file well. I like to name it with the OS, the role, then the last time I ran Windows Update. When updating gets to be too much of a pain after the creation of a VM, I will create a new image.
When you need a VM you will make a copy of this file, move the new file in to your .vhd directory and attach your VM to this new .vhd file.
Of course, there are more and more things you can do with automated deployment. Microsoft even has a very interesting program and tool kit that you can download and use to create all sorts of answer files and what not for large unattended image installs.
