When you delete files in Windows, they can be easily recovered. Windows deletes the files in the system, but they remain on your hard drive until they are replaced with new data. 
Despite the fact that on SSD, it is more difficult to recover files from hard drives, due to the ditreatmentand the garbage collection done by the SSD controller, all deleted data is not completely deleted by default.
So if you've deleted some sensitive data and you want to be sure that it can not be recovered for any reason, we'll now describe a deletion that will eliminate them forever, even without third-party tools.
In Windows XP, Vista, Windows 7, Windows 8 and Windows 10, there is a console utility called “encrypt” or “cipher”.
It is one tool command line to encrypt files using EFS (Encrypting File System). But this particular tool has an additional function. It can "overwrite" and re-wipe to the free space, so all the data it contains will be safely deleted.
To achieve this, the cipher performs 3 passes. With the first pass, it fills the empty space with zero data, the second fills the empty space with numbers 0xFF, and the final pass fills it with random numbers.
This process may take time, depending on how large your disk is and how much free space it contains.
To clear the free space safely with Cipher.exe, do the following:
In Windows search, look for cmd.exe. When the black icon appears, right-click on it and open it as Administrator.
Type the following command and press Ender:
cipher / w: C
Replace the “C” with the letter of the drive on which you want to clear the free space, and wait until it is finished.
Cipher.exe is a great way to safely clean up your free space if you really need to. Note that on SSDs, extra writes in the long run may slightly reduce the duration disk life. But the free your space will be securely deleted, and no one will be able to retrieve your sensitive files or know what activities you have done on the computer.
