Ah, ok, it's a laptop? Well, then you are right, that's not so nice using an external HDD. i never did that with my laptop either, only with my desktop PC.
For last ten years I've been using only laptops. I've decided to go for "one laptop, one system" solution. Yesterday I bought a cheep one for general/family use and I'm gonna make my old one dual boot again (with Windows left just in case, I'm not planning to boot it in the near future). The new one comes with Win 10 pre-installed and I'm positively surprised that Microsoft still allows people to setup user accounts without having Microsoft's online account.