[quote=@pugbutter]
[@Vilageidiotx] Is this something I can try now, or was it too late once the download finished?
[/quote]

The download was finished. I think it might have even installed at least partly, but I don't recall. I just came home to a Windows10 setup screen, it asked me if I was authorized to accept the changes, and I said no. Then it asked again, and I said no, so it gave up and uninstalled. 

But if you set it up, you have Windows 10. Unless it lets you roll it back, you'll have to wipe it and install whatever you had before. From scratch.