MS spends a lot of effort to keep their OS's off of USB drives because we could carry them around to any computer.
The only success ever reported on the web that I've seen is for XP and it is one of the more complicated tutorials.
Someone stops by here about once a week to claim it can or has been done, but never have any proof.
The USB is what blocks it, since you can IDE plug the same drive and its just another HD.