Booting Windows from USB is possible. But, I have never done it before. You will have to search for it. You may be able to boot from a repair CD or installation CD and get access to the drive. Theoretically, if you are able to attach another drive and then boot from CD, you may be able to copy files using the dos prompt (command console) available in the install-or-repair facility.
A bootable linux USB drive is easier to do than a bootable windows USB drive.