Files are not actually erased from your hard disk when you delete them in WIndows. They can be recovered usign file recovery software.
If you are really paranoid about your privacy, you can use software to erase files permanently from your hard drive. Such software rename files and overwrite them to ensure they cannot be recovered. In this tutorial, we will use Delete On Click, a free software, to erase files.
If you want to remove software completely from your computer, try the affordable (but paid) Secure Uninstaller – it does what its name says!
If you are on Mac OS X, follow this tutorial to erase files permanently using Permanent Eraser.
ADVERTISEMENTDownload and install Delete On Click
Download Delete On Click. Once the file is downloaded, double-click and start the install process.

You will need to click Next a few times – there isn’t any settings that you need to tweak. Once installation is done, it will ask you to restart the computer. Hit “Finish”.

Securely erase / remove files
Delete On Click runs off the context menu (that comes up when you right-click). To permanently delete a file, right-click and click “Securely Delete”. Depending on the size of your files, it may take a few minutes to delete your files permanently.