I'm a bit puzzled by this. You can install Windows without having to buy it. You can even run it forever if you want to - other than a watermark and some personalisation options being locked, nothing is different from an activated copy.
For stuff like simply configuring a device, any old ISO or even VM image available directly from MS should do.
For stuff like simply configuring a device, any old ISO or even VM image available directly from MS should do.