Can I dual boot Ubuntu and Windows XP on an internal and external hard drive

I've recently gotten a computer with no OS on it.

It has 1 internal and 1 External hard drive.

I have a bootable USB with Ubuntu on it and a copy of windows XP.

Is their a way of installing Ubuntu onto the external hard drive and Windows onto the internal HD so that I can choose which one it should boot from without having to remove the internal HD each time I want Ubuntu, and preferably without having to partition?

Currently the hard drive is blank and un-formatted but the external hard drive has not been made bootable, will this be needed?
Any websites with tutorials would be greatly appreciated.