I was working with a customer the other day who was having difficulty in getting their Windows 2012 servers activated. Come to find out the product key was entered incorrectly during the OS installation. However, they couldn’t figure out how to change it. It is fairly simple once you understand that the method of changing the product key is no longer GUI-based like it was with Windows 2008.
To make the change, open an elevated PowerShell console…
Enter the following command to remove the existing product key: slmgr -upk
Once you have your new (or correct) product key, the following command will install it: slmgr -ipk <New Product Key>
Reference(s): http://www.windowsitpro.com/article/tips/control-your-licensing-with-slmgr-100477, http://social.technet.microsoft.com/Forums/en-US/w8itproinstall/thread/35de7d1c-ba3d-4e9e-91a6-0a68fd149ccd/
by Todd Nelson