This one took me a while to figure out, and maybe I’m just bad at searching online, but the “answers” I found were infuriatingly nonsensical. I just wanted to install Windows on a MacBook Pro.
Error message from the Windows Installer:
Windows could not prepare the computer to boot into the next phase of installation.
This was because the boot media I was using had an EFI partition. Since it was empty, I’m not clear on its purpose or how it got there, but removing it fixed the issue. I’m installing “by hand”, since I can’t get Boot Camp Assistant to work - I even reinstalled MacOS and reset the NVRAM.
I have no idea what is up with this. Most of the time it fails with
-2100F, but every now and then when I’m not looking, it’ll work. I thought it might be the pi-hole, but I’ve seen it work with the denylists enabled.