Yes, you can make deleted files unrecoverable on Windows 8, 7 and in Vista. If you thought emptying the Recycle Bin will permanently delete all the files it contained, you are wrong. Even if you format a drive, the data can still be recovered. There are plenty of file recovery software solutions that can recover deleted files, making your private data open for anyone to view. This is the first thing that comes to my mind whenever I think of putting my laptop up for sale: "What if someone runs a recovery software and gets access to all my data including pictures and other sensitive bits of information?". There had to be a solution for it and there certainly is one.
Step 1: Download the utility from this page: SDelete.zip.
Step 2: Unzip the downloaded file and then run sdelete.exe. Preferably, extract to to C:\.
Step 3: Click on "Agree" button to accept the license terms.
Step 4: In Command Prompt, navigate to the directory where you placed the sdelete.exe file.
Enter the complete path and name of the file or folder that you want to delete. Your files will be permanently deleted and will become irrecoverable by any file recovery software.