CheckDisk is a powerful tool for searching and repairing disk errors. It is quite similar to the ScanDisk tool or chkdsk.exe, supplied with the Windows operating systems (Windows 2000 and higher. Under Vista with admin right).
Disk Scanner is a freeware utility to check the hard drive for read errors. It makes a raw sector read check of the hard drive and shows the result as a picture of your disk, where the bad clusters marked, so you can see status of your disk at a glance.