I saw from another post how to do this: by using
cat (optical disc device) > (ISO file on regular disk)e.g.,
cat /dev/sr0 > /z/windows7.iso
When I tried it, it goes partially then gets
cat /dev/sr0: Input/Output Error
This happens at about 20% completed on one of the DVDs and maybe 3% on the other one.
NB: these are LEGAL original Windows installation DVDs that I had successfully installed on older (now defunct laptops). It is very unlikely that both DVDs became corrupted/damaged. This has to do with the copying, not with the original media.
Here is output:
steve@mithril:/z$ cat /dev/sr0 > /z/windowsxp.iso
cat: /dev/sr0: Input/output error
steve@mithril:/z$ ll /z/windowsxp.iso
-rw-rw-r-- 1 steve steve 652869632 Jul 6 13:11 /z/windowsxp.iso