It might be worth mentioning here that cheap external hard drives are crap. I've made a practice for the last few years of using them for backups and anything else I need a terabyte drive for (mostly media storage), and in that time I've lost three of them, about one every year and a half. I haven't lost an internal drive since about 1995.

The usual point of failure seems to be the backplane rather than the drive itself, though. So the data's recoverable as long as it's not hardware encrypted.