so you want to install any Windows OS from a bootable USB key

Well this guy wrote it better than I can so so check it out, PS I have used this app and it works great.. PS this is a codeplex.com project.

http://blogs.technet.com/b/bobh/archive/2012/09/04/the-simplest-was-to-create-a-bootable-windows-server-2012-or-windows-8-usb-key.aspx

http://wudt.codeplex.com/