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. 
Although on SSD, it is harder to retrieve files from hard drives because of the SSD control and garbage collection, 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 "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 search for cmd.exe. When the black icon appears, turn 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 lifetime of the drives. But the free χώρος σας θα διαγραφεί με ασφάλεια, και κανείς δεν θα είναι σε θέση να ανακτήσει τα ευαίσθητα αρχεία σας ή να ξέρει τι δραστηριότητες έχετε κάνει στον computer.
