Read error - cannot access mp3

I have a collection of more than 30,000 mp3s. The drive they are on is full and I am in the process of moving some of them to a different drive. what I have found is that there are many of them, approximately 1500 that have become unreadable and I am not able to access them through any program. It doesn’t matter what I try, I get the same result that the file cannot be accessed. It is recognized as an mp3 but I cannot play it or modify it.
If I right click on any of them they freeze widows explorer and it was only though installing explorerxp that I am now able to move them.
I have no idea how they became damaged but i would like to be able to salvage them if it is at all possible.
I’m not sure what other kind of information would be helpful but I would truly appreciate any advice that anyone has to offer.
I don’t clearly understand what the problem is and have no idea where to go from here.
thanks in advance

If the data is really corrupted, there’s probably nothing you can do to restore it besides using professional recovery services. Have you tried to use the hard drive in another computer? This way you could rule out other problems.

Whatever you do, get the still working MP3s off the disk as fast as possible. Having 30,000 MP3s on a single hard disk without a backup is really asking for trouble…