canuck, I didn't see where you posted the edition of 8.1 you have - is it home or Pro?
in the screen TopGun posted, you'll want to download the Win10 edition that corresponds to your Win8.1 edition
It's either Home or Pro ... also make sure you download the correct
bit depth Media Creation Tool (32 bit or 64 Bit)
Playing a bit of catchup on the posts here .....
Don't select upgrade this computer, select the download for install on ....
Thanks to all you guys for your advice and support. I am going to wait until I go into town next week and re-download at a wifi hotspot there. I know which version I need in 64 bit and hopefully a new ISO will solve the problem.
Thank you all.
Please do let us know how you make out.