If the files on those cd discs are "image files" as in some sort of system image, then sometimes you can browse inside them using 7z even though windows file explorer will not usually go there.
But as for being able to suggest a precise solution to your problem, it would be really helpful to know what type of files the files are, what sort of cd they are on and whether you can remember anything about when they were originally made. You have posted this in the encryption section of the forum, do you know for certain that they were encrypted, or is it just that being unable to open them by normal means you have assumed they are encrypted, if it's the former then it might well be impossible to open the files without the passwords, if it's the latter then it's a matter probably of finding the relevant program to open the file type in question.
Also, you mention that they were made on "computers you no longer own". Unless some sort of special encryption program with some kind of "only allow this cd to be read by the following computers" function was used to make the discs then they should be able to be read on any computer, so the fact that you no longer have the computers they were made on shouldn't be a problem.
Edited by rp88, 03 September 2015 - 01:56 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB