To some, the title might seem a contradiction so let's take a moment of order. Erasing the free space on the hard disk means completely cleaning the disk part not occupied by files, of any trace of other data and files that had previously been deleted.
The assumption is that when you delete files on Windows, after emptying the recycle bin, they are not removed, simply the reference that allows the system to identify and read them is deleted.
Without going to the technician, you can imagine a trash bin where you can throw written and crumpled sheets of paper; what is written can still be read.
The files on the computer, from the moment they disappear, become free space and can be overwritten by other data.
Erasing the free space therefore means completely eliminating all the remaining data which, even if they are not readable by Windows, can always be recovered also through free programs (see how to recover files deleted from the computer),
Another distinction must now be made.
In another article I wrote about how to format the hard disk and erase all the files completely, citing a program like DBAN that eliminates all the contents of the disk integrally, making any data unrecoverable.
This time, however, we are not talking about formatting but simply about deleting the empty space, leaving the files on the computer completely intact .
The program to be used is called Zerofill which overwrites the free space on the disk and prevents the recovery of computer files.
This tool has its usefulness when, for example, you need to return your company laptop or sell or give a PC to a friend or another person, with the certainty that all personal data is no longer present and recoverable.
It is therefore a program to protect privacy, even to be used every time the computer or hard disk is thrown or sold.
Moo0 Anti-Recovery is another program, in Italian, that you can download for free and that must be installed being careful not to install the sponsor program.
The use is very easy, just choose the disk on which to erase the free space and then select which operations to perform.
These include emptying the recycle bin, deleting free disk space, free space on the Master File Table (MFT), Clusters (the end of each file) and traces of file names.
To have the guarantee that the data will no longer be recoverable, you must enable everything and start the destruction.
I do not recommend, however, at first use, to start the definitive cancellation of everything because the operation takes a lot of time.
Instead, it pays to work in stages, first one, then the other and so on.
It must also be considered that temporary overwrites occupy all the disk space.
So if you delete on the main disk (disk C), the one where the Windows operating system is, it is likely that the computer crashes during the entire working period.
However, each operation can be canceled.
In another article there are programs to delete files forever by deleting them permanently, including Eraser, which works as Zerofill to overwrite the free space by deleting it so as not to recover any files
