How can old Data be completly removed from the computer,   is
defraging a computer good enough.

Or does one need to zero the whole drive and then reformat ?  and is
that even good enough?

If you are really concerned about maintaining the security of data
which needs to be deleted, you should download a sanitizer format
utility which is able to write 0's, 1's and random bits to a hard
drive over and over again (at a minimum of 7 times, but it's arguable
to recommend at least 30 rewrites). The reason is, because of the way
0's and 1's are stored on a hard drive, it is possible, and cheap to
recover data which has only been rewritten once, or even a handful of
times. I've provided the link to an academic paper which has recovered
data from drives in various counts of rewriting/reformatting, as well
as outlining the procedure used to recover the data.

Sanitizer Utilities:
://www.google.com/search?q=sanitize+format+%22hard+drive%22+5220.22+freeware

"Secure Deletion of Data from Magnetic and Solid-State Memory":
http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html


Thank you for your question,

skermit-ga

Thankyou

Another free program I've used for years to both free up hard-drive
space and securely delete data (26 overwrites as standard):

http://www.tolvanen.com/eraser/

By right clicking the main area > then New Task > Unused space on
drive, you can completely wipe clear of any information on the "free
space" of your harddrive. This will eliminate the need to wipe
individual files and also gives you the ability to wipe previously
deleted files. Leftover information is usually left there until it is
overwritten by other information.

It also removes the useless cluster-tips on your hard-drive, thereby
safely freeing up around 25MB of space per drive.

More info:

http://www.windowsitpro.com/Article/ArticleID/42207/42207.html

http://slashdot.org/askslashdot/01/02/21/1752256.shtml