download windows 7 using torrent:
https://kat.cr/windows-7-all-in-one-pre-activated-excellent-t7661549.html

use rufus to add the drive:
http://www.techfleece.com/2015/07/08/how-to-create-a-bootable-windows-usb-drive-using-rufus/

Rufus download:
https://rufus.akeo.ie/

how to boot from USB:
http://lifehacker.com/5991848/how-to-boot-from-a-cd-or-usb-drive-on-any-pc