So you have a windows 8 key but you want to install 8.1 fresh & when you tried, you noticed your windows 8 key wont work on 8.1.
Well, here’s what you do:
Grab the windows 8.1 ISO or DVD
Boot from the 8.1 USB/DVD/PXE & install as per normal
Use this generic key during the setup process:
(note: this will fail activation, obviously)
Once you’ve installed 8.1 open up the command prompt as an administrator and type the following:
slmgr -ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
(note: the XXXX is your Windows 8.0 Product key, upgrade or retail or Volume license)
Open up your activation wizard and now your windows 8.1 should activate itself with your windows 8.0 key!