Experts will know that when you delete a file from the Windows recycle bin, the space occupied by the file is not deleted, it is simply marked as free so that another file can be written to that space. So it is only after the space is overwritten that that file, first deleted by emptying the recycle bin, is really deleted.
Otherwise it is still recoverable and that is why on a computer it is always possible to recover files deleted from the disk, perhaps by mistake.
On a computer, you can overwrite the free space on the hard disk .
The goal is therefore to really erase all the data that had already been deleted in the past, gaining disk space and making these files no longer recoverable .
Without the need for external programs, if you are using Windows 7 or Windows 8 just open a command prompt with administrator rights.
In Windows 7, click Start, go to Programs, right-click on the command prompt and run it as administrator.
In Windows 8, just press the right button in the lower left corner to open the prompt.
Then type the command:
cipher / w: F
Where F is the drive letter of which you want to free up space by overwriting the space marked as free
Overwriting occurs in 3 steps: first with all zeros 0 × 00, then with all 255 0xFF and then the third with random numbers.
After about an hour or even more, depending on how much space is to be overwritten, the procedure ends.
No data on the computer is in any way touched or deleted even if, during the procedure, it is recommended to close any other program and not to use the computer.
During the overwriting procedure, in fact, the entire space on the hard disk is occupied making it difficult to save new data.
Alternatively, even for Windows XP, an external program such as SDelete can be used.
Download the file, extract it, open the extracted folder, write "cmd" in the address bar of the folder at the top (where there is the path) and press enter.
In the command prompt that opens, write: SDelete –c F:
Where F is the letter of the unit whose space is to be overwritten.
Even simpler, you can use the Anti-Recovery program described in the article on how to clear free disk space and make files unrecoverable .
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