[Atomic-S (OP)]

I run Windows XP. How can I absolutely delete a file so that it is completely erased, leaving no residue that might be readable by someone who has full access to the disk?

[CliffordK]

If you are reformatting the drive, then run a "shredder" program or wipedisk program for the whole drive then reformat and reinstall your "clean" software.

If you are just deleting a few files, then go ahead and delete the files.  Hunt for backup copies and cached copies and delete them too.  Perhaps dump all your temp files and internet cache files,  then run a free space shredder.

[RD]

I run Windows XP. How can I absolutely delete a file so that it is completely erased, leaving no residue that might be readable by someone who has full access to the disk?

Free software from a company called Piriform can securely delete files the recycle bin / shred free-space

https://en.wikipedia.org/wiki/CCleaner

and see if any "deleted" files can be recovered ... https://en.wikipedia.org/wiki/Recuva


A free archiving program I use called Peazip https://en.wikipedia.org/wiki/Peazip has a file-shredder
[ PeaZip also allows archived files to be encrypted ].   

[syhprum]

What measures you take to destroy the files depends of course on how dangerous it would be to have them read it may be expedient to remove and destroy the disk drive but if they have been sent as emails or cloud storage there is probably no way that they can be got rid of them !

[CliffordK]

Yes, there are benefits of physical destruction of the hard drives.  Degaussing can also be used (which can also render hard drives, floppies and some tapes as permanently unusable).

A good file recovery program should be able to do a keyword search.  So, say you know a specific word or phrase that is in your document, you can search the entire hard drive for that phrase irrespective of whether it is in an actual file.  It can be quite amazing how many copies of a file actually show up.

There are also better encryption programs available.  I think newer versions of Windows (not XP) are tied to a chip that is on your motherboard, so without that chip, the drive is unreadable (I don't know what happens if you crash your motherboard).  CMOS passwords can also make it more difficult to start up the machine. 

Of course, you also have to worry about having secure backups.

[chris]

What does "shift-delete" to - as Windows promises - "permanently delete a file", actually do?

[CliffordK]

What does "shift-delete" to - as Windows promises - "permanently delete a file", actually do?

Windows does a two stage deletion.

A normal delete puts files into the recycle bin which are easy to recover the files from without any additional software.

Either emptying the recycle bin, or doing the "shift-delete" simply takes away all directory entries to the file and puts the file in the free block list.  However, it doesn't delete any of the data in the file.  Actually, it may just mark the directory listing as available, but I believe all but the first letter remains in the directory list too. 

If you don't make additional hard drive changes, a simple undelete program will recover 100% of your file except perhaps the first letter in the filename.

Symantec/Norton used to make a "shredder" program which you could dump your file into which was supposed to delete that file by replacing all data with random 1's and 0's.  And, I believe that it would effectively shred that single file. 

The problem that occurs is that it is easy to end up with many backup files on your hard drive.  Say you are composing a file using MS Word.  Each time it saves the file, it creates a new file first, then deletes the old one.  One used to have a feature to make a .bak file automatically, but I believe that may be turned off by default now.  But, you still have the original file that is removed from the directory listing, and the new file.  Part of the reason for a two-step saving process is that if the program crashes during the middle of a file save, the original file isn't destroyed.

Anyway, so simple deletion or shredding doesn't get rid of all the backup and old copies of the files.  Temp files and cache files may also be made that contain some or all of your file. 

The only way to be reasonably sure that your file is gone is to delete the original file.
Delete all potential temp/cache files.
Shred the free space on the hard drive.

Unfortunately, it is hard to guarantee that bits of the file aren't still hidden somewhere.  This is why many businesses and the government now physically destroy the hard drives before recycling the computers.

[RD]

What does "shift-delete" to - as Windows promises - "permanently delete a file", actually do?

 "shift-delete" files can be recovered : I tested this using Recuva ...

 [ Invalid Attachment ]

The more the computer has been used since the deletion, the more likely the "deleted" files in free-space will be over-written and unrecoverable.

For some reason the names of deleted files can be persistent (although their content is unrecoverable) ...

 [ Invalid Attachment ]

So if you have anything with sensitive info in the file name my advice would be use an encrypted partition/drive, e.g.  TrueCrypt .

[CliffordK]

Ouch!!!!
I didn't think about the file names being stuck in the directory entries.  A good free space shredder, or even individual file shredder should take care of that, but it would be easy to miss.

Hopefully the "security" companies have looked at ways to protect people from unexpected hiding places for the data.

[Atomic-S (OP)]

It is doubtful that there is any such thing as cybersecurity.

[RD]

It is doubtful that there is any such thing as cybersecurity.

John thinks there is ...
http://www.mercurynews.com/business/ci_24168403/exclusive-john-mcafee-vows-make-internet-impossible-hack  []