Simple answer is you can’t! (I say this so that someone will take on the challenge and solve the problem)
Can you believe that it is not possible to just buy the Windows 8 Pro upgrade which will automatically upgrade Windows XP/Vista/7 using the Upgrade Assistant and install it when running the evaluation release of Windows 8?
What on earth were Microsoft thinking when they forgot about the thousands of us who upgraded their perfectly working Windows 7 machines to get a glimpse of Windows 8, expecting to be able to simply buy the official Windows 8/8 Pro license when it was released.
Here is what I went through with a very helpful Microsoft support guy – this is the first time I have used Microsoft support and only resorted to it as there was little information on Google regarding Windows 8 Upgrading and none on upgrading the evaluation build.
If you have already downloaded the Windows 8 Pro software, I suggest you burn it to a DVD (or two) just in case. That way you can always install from scratch. The ISO contain a bootable image with all the software you need (remember to boot from DVD in your BIOS – press F11 usually on startup) – it is not some cutdown build that has to be run from within Windows.
However, it is that EARLIER word that causes all the problems. If you try to upgrade an existing Windows 8 build (remember you are running Windows 8 evaluation build 8400) the upgrade assistant will happily take your money, then download the 2.8GB file and start the upgrade process only to tell you that you are already running Windows 8 and all you can do from here on is “Add features”.
Now of course, adding features would be fine if the product key you got when buying the Full Upgrade worked to just buy those extra features but it doesn’t.
The Microsoft technician said I should have bought the Pro Pack instead (there is small print on the Microsoft site when downloading the upgrade that says which versions it will upgrade but never in a month of Sundays did I think it meant you couldn’t upgrade Windows 8 Evaluation). And get this – how much do you think the Pro Pack is? £49.99 in the UK – and this is only for upgrading Windows 8 to Windows 8 Pro!
Anyway, the Microsoft technician using remote desktop assistant tried for over an hour to get a Pro Pack license that he gave me to work to enable all these wonderful extra features but to no avail.
In the end, I was left with the prospect of either reinstalling/reverting to Windows 7 then upgrading with the upgrade assistant (assuming it could find the download on my hard drive) or as I always burn any downloaded ISOs to DVD, install from scratch using the ISO that the Upgrade Assistant created for me.
The original product key worked fine installing from scratch.
I’ll post some pictures as soon as I get time…