Below are just a few of Sanitization tools available:
Darik’s Boot and Nuke (“DBAN”)
New Technologies M-Sweep.
Paragon Disk Wiper.
DTI Data Disk Wipe.
Acronis Drive Cleanser.
East-Tec Disk Sanitizer.
LSoft Active@ KillDisk.
Think System Mechanic 4 Pro/DriveScrubber Pro
Note: most meet DOD 5220-22M Standard for Sanitizing Drives:
“Non-Removable Rigid Disks" or hard drives must be sanitized for reuse by overwriting all addressable locations with a character, its complement, then a random character and verify.”