I happen to have more than a couple of dozens Windows Server VMs in my HomeDC, starting with Server 2003 and ending with (the gorgeous) Server 2016.
I tested 2016 along with various products (including XenDesktop, Horizon View, VEEAM) since I first got my hands on the Tech Preview 1 and as per today, I have close enough to 15 VMs running with the 2016 Evaluation version. I didn’t really wanted to reinstall EVERYTHING just because Windows doesn’t want to switch “automatically” from Evaluation to the new Product Version for which I had a license, so I started digging into DISM.
So, what’s to be done?
Open an elevated Command Prompt (Win+X, then A) and type:
DISM /Online /Set-Edition:ServerStandard /ProductKey:Your-VLK-Product-Key-For-WindowsStandard /AcceptEULA
NOTICE: If you have a Datacenter edition, you might need to set the edition to “ServerDatacenter” as it was the case for me.
At the end (yeah, it takes a while…), the process might request a reboot, so reboot your server and then check the Activation status.
PS: Not sure if this works for the Core edition. Didn’t had the time to test, but I guess it’s not working.