I found one-terabyte external hard drives on sale at Costco today for $59.95, so I snapped one up. Brought it home and connected it, via its USB-3 cord, to my Dell laptop running Windows 7, then tried to copy and paste a large folder into it. It copied a few of the sub-folders, but not completely, then nothing. I must have done something wrong, but not sure what. Any help will be appreciated.