Hey Searle. The Code 10 error usually occurs when the Device Manager can't "start" the device. This could be due to a driver problem, so I'd advice you to roll back the drivers for your external HDD or update them to a newer version if such is available. You can use system restore as well to undo any recent changes that have been made in the Device Manager. Another reason might be that the HDD might not be gettin enough power through the USB port. If that's case, you should try it with different USB cables, different computers and USB ports to make sure that non of them are faulty. If that doesn't work as well you might have to get an externally powered USB hub.
Hope that helps. Let me know if you have any questions.
Boogieman_WD