How To Change Windows 8 Product Key To Complete Activation
While I was installing Windows 8, one thing I found that was missing, at least to me, was the activation dialogue.
No activation is fine and ok for me, until I wanted to change my Start screen’s background.
Under the PC Settings > Personalize. It says “You need to activate Windows before you can personalize your PC.” So that leaves me no choice but to activate.
But …
After poking around all the possible place, I just couldn’t find a UI that allows me to change or even enter my activation key. It seems like a time for a “hack” for it.Firstly, you need to go to the Start screen type “cmd” and right click. Make sure you choose run as “Administrator” from the bottom options.
Once the command prompt is launched with local admin privilege, run the following command to enter your activation key.
slmgr.vbs -ipk YOUR-ACTIVATION-KEY-HERE(If you have already installed a key, remove it by the code slmgr.vbs -upk) 
You will get a confirmation for the product key that you have entered.
Then, run the following script to activate the product key
slmgr.vbs -ato
Finally, you will get a confirmation on product activated successfully.
Now all you need to do is to restart your Windows 8.
