My laptop (Acer 5100) is not recognizing the new usb hdd. I don't know why. I have another usb ext hdd that it recognizes fine. It's a 750GB Western Dig Caviar in an Elite SATA enclosure, usb 2.0 going into usb ports that are known to be good. It just doesn't show up on the radar at all, I don't know why. All the connections fit. Any suggestions?