Then that won't be the problem.
Are you connecting it directly to the PC? Not via a USB hub? Are there other devices connected via USB to the PC? On the same hub? Try removing all other USB devices. Remove everything with the exception of the external drive and maybe a keyboard/mouse combo. Then make sure there's nothing else connected to the the hub the disk is connected to (nothing else connected below or above the USB connector where the disk is connected to), not even the keyboard or mouse.