So that files are corrupted. That means they are lost. Only copy the good files and forget about the others.
This story again proves the validity of that old saying "You only lose what you didn't backup." Having only one copy of files (documents, pics, music, whatever) on a certain device (mp3, phone, USB-stick, diskette, CD, external or internal hard disk, everything you can think of) implies that you don't mind to lose it.
If formatting the player doesn't help, it's time to buy a new one.