Installing 64 bit Windows 10 on VirtualBox headless

Wanted to try Windows 10’s Windows On Linux subsystem to see if we can test mingw built toolchain binaries using the usual Dejagnu/expect/tcl testsuite runner. First step, of course, was to get my hands on a Windows 10 ISO. I didn’t have a spare machine lying around, so I decided to try this on a VM. I had a CentOS machine available that I could logon remotely, so I yum installed VirtualBox-5.