How to Solve Error 0x8007007B When Activate Windows 8

If you get the error : 0x8007007B when trying to activate Windows 8, it is caused the product key is invalid.
This will happen, because during Windows installing process you didn't asked for entering the product key, and when activating will get this 0x8007007B error code.

So, before activating the Windows you have to change the valid product key you already purchased.

To get the menu for changing the product key :
Press Windows logo + R to go to RUN Command
Write slui 3 then click OK or press Enter