USB drive error message-wii-problem.jpg

I own a modded Wii (4 year old console) with games stored on hard drives. Whenever I've gotten the above error message in the past, it has been because the hard drive was plugged into the wrong USB port.
However, I'm still getting this message, even with the USB plugged into either port. Does anyone have any suggestions on how I can fix this? Is it possible that the USB port is busted? Many thanks.