Thank you for th suggestions.
I will try with my DVD player/TV. I did try to pursue the problem with the vendor of the DVD/CD recovery programme, but they didn't help. I too suspect that the DVD burning programme might not have done a good job and am getting resigned to never seeing the pics again.
But heh! Life goes on. The inspector will maybe dig up the septic system to look at how we constructed it, or take our word for it. Whatever. Just a pity that we lost pics.