Downgrading Licence from Enterprise to Standard Edition 2008 Serve

Hello:

I currently have the Technet eval of Windows Server 2008 Enterprise

installed and Hyper-V is configured.

I just purchased a license for Standard Edition to use on this hardware

going-forward.

Is it possible to do an in-place downgrade from Enterprise to Standard?

If so, how could I accomplish this task without losing my Hyper-V

configuration?

Thanks!