Quick notes: Microsoft Windows VM, virtualbox -> qcow

I'm going to need a VM running Windows.  It is trivial, but taking a
few notes might avoid the need of looking this up again in future
(if I ever need it again, hopefully not).

First off, the VMs are nowadays available for free download[1].
- 18 gigabytes of download! -

They have an expiration date.

  Once upon a time it was suggested to take a snapshot of them.
  Nowadays the site reports a specific expiry date.  I'm not sure the
  snapshot trick will be effective, but I guess I'll find out later.

I need to convert it to qcow2.

  I took the VirtualBox format because the conversion seems to be trivial.
  It boils down to unzip the binary, extract it from '.ova' format (which
  is just a tarball), and then use qcow-image(1) (with 'convert' command):

  $ qemu-img convert -f vmdk -O qcow2 file.vmdk file.qcow2

[1] https://developer.microsoft.com/en-us/windows/downloads/virtual-machines/