So you shouldn't need to do this but in my case for some reason I needed to activate windows after performing and upgrade from Windows 8.1.
In my case I tried activating Windows by clicking on Activate Online and that didn't work for me. I managed to activate Windows 10 by entering the product key for enterprise.
Windows 10 Pro Key: NKJFK-GPHP7-G8C3J-P6JXR-HQRJR
Windows 10 Enterprise Key: PBHCJ-Q2NYD-2PX34-T2TD6-233PK
You can download bat files that set the key from my GitHub gists using the links below
Activate Pro Gist: http://beeming.net/gist/fc85f772fbc35c470f7d
Activate Enterprise Gist: http://beeming.net/gist/b49470b9ba1cf861d56c
You should be able to find these on the preview site as well. Hopefully this is useful for someone else as well