Hello and welcome to the forum.
I think you'll find that as a general rule and concensus, Microsoft does not support the installation of their Operating Systems on what would normally be considered "removable media", with the exception of Windows To Go which they suggest only be used with their Enterprise version.
There are a number of suggested work arounds on the net but they've always seemed to me, to be overly complicated and hardly worth the bother.
I guess if you are determined enough you might have a look around
http://www.techspot.com/community/t...windows-on-an-external-usb-hard-drive.116114/
OR in the case of Windows To Go
http://www.howtogeek.com/196817/how...-go-usb-drive-without-the-enterprise-edition/
There are probably many others. None of which I've personally tried although someone else may have first hand experience.