As you might know, the applications that promise you to completely remove the content of your hard disc tend to leave traces that can later be recovered. In this way, if the deleted information was vital, the user that managed to restore it will have access to the private information.
In order to avoid this, there are applications such as Active KillDisk that unlike other utilities can really delete all the information of any hard disc or magnetic storage device.
This software has a direct and easy-to-understand working, provided the user has basic MS DOS knowledge, since this utility is fully designed under command lines.
With Active KillDisk you just have to upload a copy of this utility in a diskette and run it in DOS mode, of course.