Diskettes, especially those not used in years, have a horrible habit of fouling up. Let's face it, disks have a horrible habit of fouling up anyway. Perhaps at some stage they have gotten warm and cooled down rapidly, or come close to a power source. Disk 2 of my 3.1 setup died, so I just did a google search and downloaded me replacement set (which is not illegal, I have the original disks, and the manual even advises that the user first makes a backup of the workbench diskettes).
I expect I'm not allowed to provide any links here, but it really shouldn't take much more than 5 minutes to obtain what you need through a search engine.
