I was installing Windows 8 today and I was poking around when I took a look at Windows activation. I wanted to put my key in but didn't see where to do that. All I saw was a message saying:
The Software Licensing Service reported that the product could not be activated. No Key Management Service (KMS) could be contacted. Please see the Application Event Log for additional information.
WTF is that? Why is it erroring out when I haven't even tried to enter a key? Stupid Windows 8!
Anyway, I found a solution. I am using the classic desktop with Windows 8 Start Button, so I clicked on Start > Run and typed in SLUI.EXE 3 then clicked OK. After doing that the window to enter a key opened up.
After entering my key and clicking activate, activation worked like a charm!