You could use this thirdparty software Download RightDelete 3.0 Free - A tool that will help you securely delete files. - Softpedia
Or download Sysinterals/Microsoft utility SDelete
place it in the C:\Program files\
And run the following reg-file.
Windows Registry Editor Version 5.00
@="\"C:\\Program files\\sdelete.exe\" \"%1\""
This will create a right click menu for all files.
When clicked on that menu files will be securely deleted (no way to restore).