Is it possible to boot from a usb on your windows partition?

Forgive me if there is already a thread on this, but most of the search results that I got were people trying to install windows via a usb stick on bootcamp.

The question that I have, is can I boot crunchbang from a usb flash drive once selecting my windows partition?

More specifically...I have a copy of vista on my 2nd partition that I installed via bootcamp. After selecting windows, is there something that I can do to boot from a usb device? I was under the impression that if I hit F2 there would be an option to boot from cd or device, but I don't get any other options when I do that.

I used this guide to create my bootable device, but I am not sure how to run it.
http://www.pendrivelinux.com/crunchbang-linux-flash-drive-install-windows/