Glad to report that it works! Just like dproberts55 above me, I used a Win7 retail disc and did a clean reformat. I did not enter a serial number and left the OS on 30-day trial mode.
I went to the Windows 8 upgrade page and downloaded the Windows 8 Upgrade Assistant and made the purchase from there.
My guess is that the Upgrade Assistant never checked for a product key!!
This is great news especially since I've never owned a Windows OS (had a volume-licensed WinXP then a pirated Win7 in my teens). Feels good to finally have a legit OS for my homebrew.
I was able to burn my DVD ISO and do a clean reformat using that Win8 disc.
Thanks to dproberts55 for posting his results and making it known this is even possible.
To Microsoft, thanks for letting the few of us that have been too broke to afford your excellent OS finally get on the bandwagon. Now that I have Win8 Pro, I won't mind shelling out another $40 for Win9 in a few years. Microsoft now has a new loyal customer..
I almost forgot to mention, after I entered my payment information (credit card number, billing address) and clicked the "make purchase" button (or whatever it says), the Upgrade Assistant said that the purchase could not be completed. So I clicked "back" (you're never supposed to do this) and rechecked my payment information (card number, etc.). I clicked "make purchase" again and again it failed. I then used a completely different card and the purchase went through. I later checked my checking account via online banking and I had BEEN CHARGED THE FIRST TWO TIMES!! YES, THE FIRST TWO THAT HAD SUPPOSEDLY FAILED!
I don't know if anyone else has experienced this or will experience it but those 3 charges, each for $39.99 work out to being just under the price for
Windows 8 "System Builder" DVD on Newegg for $140!
I called Microsoft and they politely informed me that I'll be given a refund (seriously, bless them, they're too good to us) but I wondered if this was Microsoft's way of getting close to fair market value for their new OS..
I'm just happy I got Win8 Pro.