If Surface Scan in Techtool Pro finds bad blocks, there are basically two options.  

Be sure to back up all data before proceeding!

1. Replace the drive with a new one that has equal or greater storage capacity. This is the recommended option.

2. Reformat the drive and zero all data.

Modern hard drives have a spare sector pool where bad blocks are recorded to prevent the drive from writing to them. In some cases, this pool can become full, causing Techtool Pro to detect bad blocks during a Surface Scan. If the disk is erased by writing zeros to every sector, it causes the pool to be rewritten. In some cases, this can free up space and restore the drive to normal operation.

However, if writing zeros to the disk doesn’t resolve the bad blocks, the drive will need to be replaced. Keep in mind that this method is typically only effective when there are very few bad blocks and is often a temporary solution. For this reason, it is recommended to replace the drive that is reporting bad blocks with a new one that has equal or greater storage capacity.