When you delete a file, the operating system does not really remove the file from the disk, it only removes the reference of the file from the file system table. The file remains on the disk until another file is created over it, and even after that, it might be possible to recover data by studying the magnetic fields on the disk platter surface.
Before the file is overwritten, anyone can easily retrieve it with a disk maintenance or an undelete utility.
There are a few easy and effective ways of getting rid of that file once and for all.
Here I am introducing you two free Tools that Overwrites and clears the free space [your old secret or sensitive data] on your hard drive
It Overwrites specific files
How to Use Eraser:
1.Once installed, right-click on the condemned file
2.click on the Eraser icon
We can choose how many times you want to overwrite the file
Download link http://eraser.heidi.ie/download.php
2. CCleaner (Windows)
By using CCleaner, we can erase specific areas and applications on your computer
Download link http://www.piriform.com/ccleaner