Disk Scanner is a free tiny utility to check the hard drive for read errors.
Disk read errors may be the first typical sign of the possible disk failure. Ariolic Disk Scanner makes a raw sector read check of the hard drive and shows the result as a picture of your disk, where the good and bad clusters marked, so you can see the status of your disk at a glance.
Red blocks mean the disk clusters with read errors.
Disk Scanner will show you the files with read errors, so you can try to restore them with file recovery software, for example Complete File Recovery.