Oh man, this shit has taken me all afternoon to figure out. Here's the ironic thing. MSI provide a tool to integrate the USB3 drivers to a win7 bootable. It didn't work on the MSI motherboard, but it worked on the other machine with an ASUS board.

This is the fucker:

https://forum-en.msi.com/index.php?topic=261560.0

The happies to see the 'configure the hdd' screen with a win7 usb on ANY of my hardware was like, omg, so much 

# BOOOYAH! 

Owned my shit, finally.

Cancer doesn't earn me 8 euros a day, a very decent amount of money in this territory.

Once I have one installation set up, it should not be hard to plug it into the other bastard thing and make it work. I am so relieved. The first one I got to work, is the one that doesn't have a windows 8.1 driver for the two amd rx580 cards in it. So now, I have my miner sorted. You know, windows 10 wasn't actually starting up my miner app automatically. It was working before. They actually made an update that was a downgrade. Unusable. 

Now to test it on my other MSI mobo with the ryzen7.