For some unknown reason, the Windows installer doesn’t let you install to a USB key. Luckily, there’s a simple workaround. It turns out that only the very first step of installation cares about that. So, if you can fool it (say, by running in qemu), you can have a USB key with a Windows install rather than having to dual boot on your hard disk (e.g. if you run Linux and want all that fast in-built SSD space for Linux)
- Download the Windows Installer: https://www.microsoft.com/en-au/software-download/windows10ISO
- Start the installer in a VM, with the USB key passed through to the VM as the hard disk (or use a disk image the same size as your USB key for transfer with a utility such as ‘dd’ later). e.g. do:
qemu-img create -f raw win-installed.img 50G qemu-system-x86_64 --enable-kvm -m 8G -cdrom Downloads/Win10_1709_English_x64.iso -hda win-installed.img -boot d
- At the first reboot of the installer, instead of letting it boot, stop the VM. You are going to copy the install at this state to the USB key.
- Boot from the USB key, go through the rest of the installer. You’re done!