I had a similar problem with my floppy drive on my computer which I currently own. It could read just fine, but any attempt to write to disks was disastrous. It couldn't format disks at all. I replaced the floppy drive and no more trouble. I sort of suspect the original floppy drive was defective from the factory, but it took me awhile to finally replace it. Did you ever try replacing the drive on that old computer? I don't know how much floppy drives cost back in those days, but you can get them for a song now.
