SDelete
When you delete a file, Windows removes the index for the file and prevents the operating system from accessing the file’s contents. However, an attacker with direct access to the disk can still recover the file’s contents until it has been overwritten by another file—which might never happen. Similarly, files that have been EFS-encrypted leave behind the unencrypted contents of the file on the disk.
With the SDelete tool, available as a free download, you can overwrite the contents of free space on your disk to prevent deleted or encrypted files from being recovered.
Additional information: “Get 7 Free Tools for Managing Disks and File Systems“
