My external HD shows me the files but won't let me open or copy them. This is actually an improvement as an hour ago every computer I connected it to claimed it doesn't recognize the USB device... It's an Iomega HD and I'm using an HP laptop, if it helps. I should mention that the HD is a bit old (about 5 y/o).
The disk manager says it's healthy, but when I run an error check it says it found errors I should fix but doesn't tell me how to do so.
Do you hear the drive spinning without any strange noises? Do the copying process even starts when you try?
Try using the chkdsk /r,/f commands from the CMD to recover some readable information. If after that you are able to copy your files, do so and format your drive. If it is a bit old device, I would say that it may not be so reliable as it used to be and you should keep another copy of your files.