I bought a Seagate 1TB Expansion External Drive under a month ago. It was working fine until a few days ago it decided to stop working. The harddrive's light blinks when loading up and then stays on when it's finished. (This is normal) Windows beeps when it is plugged in recognising it. So the harddrive is picked up by windows somewhere. Under a minute, i havent timed it, it freezes my computer completely, except for my mouse. My computer does recognise it. And it shows itself in device manager as a USB Mass stoaage device now. Before it was Unrecognisable USB Plug.
Try it on another computer and see if it does the same thing to that computer. If it does, it is definitely an issue with the the drive. In that case, I'd return it or call the manufacturer and request a new one (they usually come with a 1 year warranty).