Use Secure Deletion Shredder for Permanent Deletion
Secure Delete for Macintosh
A Secure Delete feature is built into Machintosh OS X computers. To access this feature, go to the Finder, select "Secure Empty Trash..." which is immediately below "Empty Trash..." from the Finder menu, and click OK.
Note: If there is nothing in the Trash, the menu item is grayed-out.
Secure Delete for Windows 7 & 10
Secure Deletion Shredder puts a new icon on your Desktop, which you can use to destroy files and folders immediately and permanently* in a secure manner by dragging them to the icon (below). Download the Secure Deletion Shredder for either operating system from Software Central.
*Note that the Secure Deletion Shredder works well only on hard disk drives (HDD). It does not work with solid state drives (SSD). To secure a SSD, apply full disk encryption.
You may select “run” or “save” to your Desktop. If you save it to your Desktop, double-click on the file to install it. There is a one-time confirmation of the license terms for the software that pops up the first time you use it.
Drag any file or folder to the Secure Delete Shredder icon, and drop it in to delete a file or folder permanently -- only if you are using a hard disk drive.* A message will pop up and ask you if you are sure you want to delete it. If you are sure, press Enter. If you are not sure, click on the X in the upper right-hand corner of your Secure Deletion Shredder Window, and close the shredder.