It recently took me 6 hours to complete a scan on a 40 GB hard drive that was donated from a system I worked on a while ago because the drive had bad sectors.
The scan found and recovered 4 bad sectors.
HDD Regenerator by Dmitriy Primochenko was the tool used for this task.
Note: The trial version will only recover the first bad sector. You will need the full version if there are additional bad sectors.