I have a WD external HD that I keep all my music on. I normally use it with my Macbook Pro. I have a coworker whose PC laptop had some MP3 files on it that I needed. I plugged in my WD HD to his PC and copied all the files over. I then ejected and plugged the WD HD back into my Mac, went and created a new folder on the WD HD, and tried to move all of those files into it. Some would not move. Some did. When I try to move them, it prompts me for my admin password. I enter it but nothing changes. I eventually copied them to my desktop and then successfully moved them back into that folder, but I can't delete or move the original ones I copied over. The folders show that I do have read and write permissions. Idears?