I have been using teracopy to verify and the large movie files show artifacting after transfer and fail checksum, small files do not fail, only large files seem to. When I transfer files off the external hard drive no such failure of checksums occur on any of the files, could this be a bad cable, or maybe a bad external interface or esata interface on my computer, I have tried two interfaces for esata, one with a pci card the other on the motherboard, both with similar results, so what maybe the reason if a bad hard drive or external case maybe the problem?