Hi there garov,
Was the drive attached to a port that supports USB 3.0?
You can test the drive with some of these tools:
http://www.tomshardware.co.uk/forum/282651-32-best-diagnostic-testing-utility
Look for pending/reallocated sectors. In case there are some, you will need to contact the place where you got the HDD form.
Apart from that, I would say that internal drives tend to be more reliable.
i forget to say that when external disc was working power has shut down. maybe is that?
Cheers,
D_Know_WD