Install Windows 7 onto AM4 Motherboard with only USB 3.0 ports
This assumes you are using a USB keyboard/mouse and your motherboard only has USB 3.0 ports. Windows 7 Installer does not support USB 3.0 input and you will be unable to progress past the language select screen. Use one of the following options to Install Windows 7 on your USB 3.0 motherboard. PS/2 keyboards and mice will work fine. This author is uncertain if there are any AM4 motherboards with USB 2.0 or PS/2 ports.
1. Disable xHCI in BIOS
If this is an option, it will tell your USB 3.0 ports to behave like USB 2.0 ports. Easiest option, if it is an option.
2. Check Motherboard product page on manufacturer website for media creation tool
Assuming you have the appropriate ISO, the manufacturer will likely have a media creation tool that will mount an ISO to USB and incorporate the drivers necessary to allow Windows Installer to support USB 3.0 You may also want to try a different applicable manufacturer's website and attempt media creation with their tool.
3. Manually incorporate USB 3.0 drivers into Mounted ISO
Follow this guide: How to Install Windows 7 with only USB 3.0 Ports (archive)
Pay close attention to step one and make sure your motherboard is compatible with the USB controller you select.
BACK UP YOUR WINDOWS 7 ISO!
Enable Windows Update for Ryzen hardware
By default, Windows Update will not support Ryzen CPUs. Windows Updates KB4012218 and KB4012219 do a scan of your hardware and prevent you from downloading updates released past March 16th, 2017. This section outlines how to bypass this restriction with a simple patch.
Bring Windows 7 to the latest updates available without the patch.
There will be some updates that will download. Install them and reboot. We need them in order to allow the patch to work its magic. If you attempt to run the patch in step b), you will get an error that Windows is not of the proper version.
Download the wufuc patch by zeffy
Download the wufuc patch and run it. This will disable Windows Update from registering your Ryzen CPU as Unsupported Hardware.
Restart and update
At this point, you should restart your computer and run Windows Update without the Unsupported Hardware warning. If everything has been done correctly, you will be able to use Windows 7 until Microsoft plugs this hole, or Windows 7 support is dropped in 2020.
Good luck!
Written October 3, 2017
The above edited text is from a Pastebin (2017-10-03 revision (archive)).
