possible?
yes: how?
no: :(

I looked on google some, and it looks like there should be a way to enable usb booting, on motherboards that support it, in the BIOS.  Have you checked there?

On my bios, I have "usb" on my "boot from" menu ("hard drive", "floppy", "cdrom", "usb").  But Windows refused to install on USB, and wouldn't tell me why.  It recognized and partitioned it fine, but wouldn't install.