Once you have your data in ISO format:
If you have a CHD made from a scratched disc, converting it back to ISO allows you to use disc repair software to attempt sector recovery. convert chd to iso repack
This article explains how to convert CHD (Compressed Hunks of Data) files to ISO images for repacking or archival use. It covers what CHD is, why you might convert it, preparation steps, the conversion process (two common methods), and tips for repacking into a clean ISO. Once you have your data in ISO format: