I had a DVD+DL that had 2 bad sectors. I had trouble copying a 4.8 GB ISO file from it because of this bad sector problem. I later thought of copying the entire DVD to another DVD+DL. Nero copied it without even mentioning about the existence of bad sectors. I then tried to copy the ISO that i had trouble previously but to my surprise i was able to copy it without any problem. I ran nero surface scan on the newly Created DVD+DL and it had no bad sectors. .Did nero do any corrections to those bad sectors ?
The data on the bad disk was read without errors apparently. Some programs can be set to retry reading sections that are bad, and this will work on occasion. And trying a poor disk in several drives is also recommended, as drives vary quite a lot in their reading ability.
One of the best programs for reading disks that have deteriorated is called ISOBuster. There is a free version of this program which will work for most types of data. The paid version is slightly more versatile regarding the file systems it will work with.
By the way, the only double layer disks that we recommend using are made by Verbatim.