از Help خود WinRAR:
Archive repairing consists of two stages. First, the damaged archive is scanned for recove ry record (see the r r command). If archive contains the previously added recovery record and if damaged data area is continuous and smaller than error correction code size in recovery record, chance of successful archive reconstruction is high. When this stage has been completed, a new archive is created, named as fixed.arcname.rar, where 'arcname' is the original (damaged) archive name
If damaged archive does not contain the recovery record or if archive cannot be completely recovered due to severe damage, second stage is performed. During this stage only the archive structure is reconstructed and it is impossible to recover files which fail checksum validation, but it is still possible to recover undamaged files which were inaccessible due to a corrupt archive structure