Upgrading Windows 2008 R2 editions from the command line
This in fact wasn't possible until Windows Server 2008 / Windows Vista SP1 which introduced ( using a built-in utility called the Deployment Image Servicing and Management (DISM) tool which doesn't require any media to upgrade the edition and just needs a reboot. I've recently had to do this with Windows 2008 R2. You can't use this on DCs, can only do upgrades, not downgrades and the supported...
Read more...