There are three main data sanitization techniques for the hard drive storage device. There is the physical destruction of hard drive where the drives are crushed or platters damaged to an inoperable state. The degaussing of a hard drive removes all data through the use of a powerful magnetic field. The third technique is overwriting of data contained on the hard drive.
There is no necessity to wipe off files on a computer if the hard drive is going to be degaussed and or destroyed.