Things to try:
1. Use this disk on another PC. Does it work?
2. Use this disk on another USB-port on your PC? Does it work?
3. Copy a few of the music files to your hard disk. Do they work?
4. Copy a few of the music files to a USB-stick and play them on another PC.Does that work?
If none work, these files are corrupted. Then restore the original uncorrupted version from your backup.
Tips to handle files on an external disk:
1. NEVER use an external disk as the <i>only</i> storage for files. Such disks are UNRELIABLE. Always keep another copy (or two!) at some other place.
2. If you're sure you don't want to change the file (such as music) set it read-only.
3. Be sure the disk has a NTFS filesystem, not a FAT32 one, if you only want to use it on PC's with Windows XP or higher.
Sorry if nobody ever told you about these 3 basic points.
I have an external drive with all of my music on it, and I plugged it in via my laptop docking station, and the check disk window popped up. I ignored it the first couple times, but I eventually thought it was important enough for me to go through with. I ended up doing it, but it got stuck on one file for over a day, so I ended windows explorer, restarted and continued on with my day. I just now had time to listen to music, but none of the files will work! WMP says it cannot play the file because it might not have a codec, VLC or iTunes won't even attempt to load it. Also when I look at a file, all of the metadata is gone. What happened and what way can I fix it? I have all the codecs because they were recently working.
I posted in the external drive forum, but I realized it should be here, so sorry for the double post.