I over wrote (I mean, saved a blank file over the real file) a file
that I didn't mean to. I have tried several recovery programs, but
none work, because the overwritten (blank) file is not deleted.  Is
there a program that would let me select the blank existing file, and
it look for all previous versions/modifications of that file?

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Clarification of Question by jacobbontrager-ga on 01 Sep 2005 00:00 PDT

the overwritten file is an export of my all my email, from Outlook. 
it is a DBT file.

I doubt it, but just out of curiousity, what program did you use?

Program, meaning the program you were using to write the files and
overwrite them, etc.  Notepad, excel, etc.

Assuming you know something about the content of the file you're
looking for you may be able to find (some of) it on disk.  English
text is one of the easier forms to recognise and recover.

A few months ago someone I know reformatted a laptop then reinstalled
the OS and afterward realised there had been files on the disk that
needed recovery. Using simple text-recognition techniques I was able
to read quite a lot of email and  text from word-processed files - but
not recover any entire word-processed documents.

Your first step in this situation should be to copy the entire raw
disk to somewhere safe using an independent tool like knoppix. Running
programs on the affected computer risks damaging the remains of your
file that may be there.

Try to use Easy Recovery Pro as it has a feature to correct corrupted
recovered files of MS office suite and also Notepad.

It depends on the blank file, if it's just an empty file, the data
should still be on disk. If you mean with blank file a file the same
size as the original containing zero's or spaces, you're pretty well
lost.
A good and easy way to see if you data is still on your disk is boot
from a knoppix cdrom (knoppix is a free bootable linux distro, it
doesn't make any alterations to your harddisk when you boot from it.
When you have booted knoppix, click on the pinguin (bottom left) and
find "Root terminal" (I believe it is under
knoppix). Now assuming the data was on your C:\ drive type
cat /dev/hda | less
(Use /dev/hdb for D:\ and so on ...)
You will see the screen fill with words from your harddrive
type /someword
to search for someword in you original text
type "n" to go to the next occurance of "someword"

Instead of knoppix you could also burn the "Auditor Security Collection"
also a bootable Linux distro and use the program "Autopsy" it's a webbase
utility to recover your data

There are also professional companies out there that could help you, I
work for a Company we run called Lostfiles we can recover virtually
anything, there are also extremely sophisticated programs out there
that police forensics etc use one for instance called Encase which
would certainly recover your file although I think it's very doubtful
you would be able to get your hands on a copy. If you have no luck
with the conventional programs you can download feel free to email me
at jamie@lostfiles.co.uk and I will see what I can do but whatever you
do it's worth mentioning not to write any further data to the media to
try and maintain the most data integrity possible. So if you require
any further assistance then please drop me an email and i'll get back
to you asap.

Regards
Jamie Bowstead
Lostfiles - Futurelab Ltd

I've recently written a column about recovering deleted files. Check
out the text here:

http://www.andybrain.com/archive/deleted_files.htm

If file recovery software can't help you, your options are to look for
a service, or to use a sector analysis tool like the "Disk
Investigator" program I mention.

Andy

if you have win xp, use system restore

I don't think System Recovery would restore an exported dbt file
unless you made a full backup. If you have an Exchange server your
mailbox info may still be available on it as a .pst.  You might also
check your email archive.  If you right-clicked on folders like Sent
and Inbox and set the Auto-Archive settings, your old emails will be
in the archive file in your Application Settings, Microsoft, Outlook
folder.

For future reference, turn on timed (set 3 min) temporary files, and
automatic backups (different file extension) in Word, frequently
export, save as, or archive your email to filenames that include the
current date and if a Windows 2003 Server is available, set all your
work to be stored on the server on a Share with Vol Shadow Copy
enabled.  On such a server you can restore all previous versions of
your files yourself, even if the same filename is used, simply by
right-clicking and choosing the previous version you want.