um you can get a windows 7, 8.1 or 10 (professional) license from here
for less than €15. I don't know if they are on sale or whether it's a permanent price (could be a partnership or something). Anyway... the licenses are just licenses they don't come with windows installers / iso (you would need to get them from windows or elsewhere).
You can always obtain naughty copies too, if you don't mind doing so.