Troy updated Windows 10 on his Mac and liked it so much he deleted macOS and now it's not working well. He's trying to reinstall it, but he can't. Leo says that's because he needs the Apple drivers through Boot Camp to run it. So he kind of has to have macOS on the computer, but he can shrink down the partition to as low as it can go. It could also be an issue with the EFI Master Boot recorder.
Here's how to fix it: http://fgimian.github.io/blog/2016/03/12/installing-windows-10-on-a-mac-without-bootcamp/. Here's another suggestion: https://www.quora.com/How-can-I-install-Windows-7-on-a-Mac-Pro-without-OS-X-or-Bootcomp
The issue is that without Boot Camp, Windows can't detect a BIOS that Boot Camp emulates. So without macOS, he'll be out of luck.
Troy also uses Google Play Music but when he uploads his music, it never finishes uploading. Leo says that's because there are some files he can't download, like iTunes songs that still have copyright protection.