How to upgrade from Windows Server 2008 to Windows Server 2008 R2 with Hyper-V......

Basically, there are three possible methods to do this:

1. Perform an in-place upgrade of the parent partition from Windows Server 2008 to Windows Server 2008 R2.
2. Migrate to another server: Export a virtual machine from a Windows Server 2008 server that has Hyper-V enabled, and then import it to a server that has Windows Server 2008 R2 with Hyper-V enabled.
3. Backup and Restore to new server: To use backup software that uses the Hyper-V VSS Writer, back up a virtual machine that is running on Windows Server 2008, and then restore it to Windows Server 2008 R2.