It should certainly not be that difficult to do copy those files; try this:
Instead of drag/drop, open a command prompt and copy, say, all files that begin with 'N' and see how that goes. Something tells me the GUI is getting in the way.
If that fails, it is possible there's a read problem with the drive. It *will* read, but has to jump thru hoops to do so. I think that's clear?