Setting up hyper-v without losing the os currently on the machine

Is it possible to set up hyper-v on windows server 2008 without losing the os that's currently installed? + how about external drives?

From serverfault Lieven Cardoen

• Erm...yeah, it's just a role that you add to a Server 2008 box anyway, so yeah, can do.

  You do mean using the existing Server 2008 installation as the 'host' right?

  Lieven Cardoen : Yeps, or changing the existing Server 2008 installation to a virtual one?

  Chopper3 : Well it kind of does virtualise it anyway to be honest.
  From Chopper3

• I think that I could rephrase your question as follows:

  I have a machine running Windows Server 2008. It's doing something interesting. Now I want that same machine image in a VM, and I want the physical hardware to be running Hyper-V. Once I do that, I want my VM to have all the properties of any other VM, including the ability to save it, move it to a new host, etc. How do I do that?

  You need to use some virtual-to-physical migration tool. If you have System Center Virtual Machine Manager, use that. If not, I'd suggested disk2vhd from SysInternals. (Use a search engine to find it.)

  You can either take images of those external drives that you mentioned and convert them to VHD files or you can configure them as "pass-through" disks for the VM. If you convert them to VHD files, you'll have the ability to move your VM from one host to another. If not, then your VM is really only partly virtualized.

  After you have the images for your VM, wipe the box clean and install Windows Server 2008 again and install the Hyper-V role. (Whether you can use the same license depends on which version of Server 2008 you bought.)

  Lieven Cardoen : So I will need to make images? I cannot just install the Hyper-V role and convert the existing installation to a VM?

  John Gardeniers : +1 for a great bit of translation. No way I could have come up with that based on the question as asked.

  Jake Oshins : Right. You cannot simultaneously turn an image into a VM and use it as your hypervisor. The question is often misinterpreted because Hyper-V itself employs a VM to run management tasks and device drivers. This is not the VM that you're trying to create.
  From Jake Oshins

• run disk2vhd then native boot the resultant vhd partition and add the hyper-v role to this!

  Jake Oshins : Are you sure that this would accomplish anything? I think that would just make your boot process a little more complicated. You'd still be running one OS. You'd still have only one boot image. And you've have zero VMs that could be saved, restored, migrated, etc.

  tony roth : yep doesn't add much to the overly contrived situation, but booting vhd's is cool anyway!
  From tony roth