I found some old backup file CDs I made several years ago. I needed to know what was one them. Well, if I could get my computer to read them. Knowing the date they were recorded, I knew why they couldn't be read. Several years and 2 or 3 computers ago, I had Nero burning software for burning disks. Big no-no, but I didn't know it at the time. Nero was good at buring, but I would find out with a new computer, that it proprietary. It uses a method of burning that cannot be read by other computers unless they have Nero installed. To get around that, they do provide a reading program that I have had to download and install on at least 2 computers. This time I pulled off all the files I want to keep and will reburn them to a new disk and also back up on EHD.
So this is a heads-up. If you're not using Nero, don't start. Almost nobody likes software that is written in a proprietary mode that makes its output unusable by other software, when that is the expected outcome.