I'd tried to play three of my .iso files in VLC, MPlayer, etc., and none of them would do anything.
I extracted the three - turns out they were corrupted files. They played back really choppy once extracted, a couple of them wouldn't play back at all from the extracted folder.
I tried a fourth .iso file after that yesterday, it worked. Played back OK.
I'm suspecting a very old USB drive that they're on is wearing quickly.
I'm sorry folks. I had no way of knowing.
So, I've just lost a lot of movie backups looks like. I still have to go through the rest of them. If there's any others that are still good I'm going to move them to a newer drive. The sad thing is some of these through my trials in life I don't have the original dvds for any more, I lost them. Those will be lost for good, looks like.
