Bootcamp Upgrade to Windows 10 Hangs on Logo

Hello all!

I'm trying to install a functioning copy of Windows 10 in Bootcamp on my Mac Mini. The problem is that when I try to upgrade from Windows 8.1, the process hangs at the Windows logo midway through the process and won't budge for days. I've tried it three times.

I'd do a fresh install, except I need to start from Windows 8.1 so it will recognize my key (Upgrading via https://www.microsoft.com/en-us/accessibility/windows10upgrade)

OSX was all up to date before I started the process. Any idea what I can do to prevent this?

Thanks!