In most cases, TechTool Pro is able to map out a bad block. On some occasions, however, the bad block may reside on a portion of the drive in which the disk drivers will not allow software to access. In this case, the only cure is to allow the driver to perform the mapping through a low-level format. First back up all data. Using Drive Setup, or another drive formatter, reformat the drive with all checking and mapping options enabled.
