"Everybody who owns a computer will someday need to dispose of a
disk drive. Before you do, it is a good idea to cleanse the drive,
so no one can read your sensitive information. Deleting files and
reformatting is not sufficient; determined effort can still reveal
data from a drive even after it appears to be gone. To do a more
thorough job, I suggest using wipe.
"You need to take special pains because files that are 'deleted'
are not really gone. Most operating systems, including Linux and
its ext2 filesystem, just delete the pointer to a deleted file; the
data still exists on the drive. It is not effectively removed until
every bit of the space it was occupying on the drive has been
overwritten. Even then there are ways, albeit difficult, to analyze
the drive and extract data. The only way, short of melting the
drive, to ensure the data is gone for good is to overwrite the
drive several times with random data..."