Did you install Launchbox on your external, configure it on your external and have all your ROMS there as well?
I'm trying to build a single HDD that I can clone for my 3 computers so I don't have to pull the information off my NAS
That way if I'm going to a friends house, I can grab one of my HDDs and plug it into their PC and just bring a controller and launch it rather than having to lug my whole rig around.