Did You know that you can add a VHD disk to your windows 2008 R2 Server and /or boot from it ?
You can easy edit the VHD and reuse it in hyper-v.
So go to disk manager and right click on disk management 
You can create a new VHD. 
If you use dynamic make sure you have the disk space that u needed.
I use a fixed disk with windows 7 on it. that I use in hyper-v as golden Image for my desktops.
fill in the VHD location. 
You can make it read only if you need software install that is on a VHD, I have a VHD with all the ISO files on it that I can mount on every server if I need to install extra software or tools.
But now I use the Windows 7 VHD 
now that I mounted the disk I can use it.
I need a WallPaper on the windows 7 
now I can do a offline or detach vhd , If I don;t I get this error in hyper-v
even if the disk is offline 
You can also delete the VHD 😉
or You can boot from the VHD it is just like in windows 7 mount it and use bcdedit to change the boot string.
below are samples.
bcdedit /set {GUID} device file=[c:]vhdwin7.vhd
bcdedit /set {GUID} osdevice file=[c:]vhdwin7.vhd
Here are some articles and video about booting from VHD.
http://blogs.msdn.com/cesardelatorre/archive/2009/01/11/windows-7-natively-booting-from-a-vhd-virtual-pc-image-file.aspx
Inside Windows 2008 R2 Virtualization Improvements and Native VHD Support (Mark Russinovich)
http://www.microsoft.com/emea/teched2008/itpro/tv/default.aspx
