Some truths about degragging
defrag
Some truths about bad sectors and disk media
bad sctors
hdd
media
The magnetic surface of each
platter is divided into many small sub-micrometre-sized magnetic
regions, each of which is used to encode a single binary unit of
information. In today's hard disks each of these magnetic regions
is composed of a few hundred magnetic grains. Each magnetic region
forms a magnetic dipole which generates a highly localised magnetic
field nearby. The write head magnetizes a magnetic region by
generating a strong local magnetic field nearby. Early hard disks
used the same inductor that was used to read the data as an
electromagnet to create this field. Later, metal in Gap (MIG) heads
were used, and today thin film heads are common. With these later
technologies, the read and write head are separate mechanisms, but
are on the same actuator arm.
Hard disks have a mostly sealed enclosure that protects the disk
internals from dust, condensation, and other sources of
contamination. The hard disk's read-write heads fly on an air
bearing which is a cushion of air only nanometers above the disk
surface. The disk surface and the disk's internal environment must
therefore be kept immaculate to prevent damage from fingerprints,
hair, dust, smoke particles and such, given the sub-microscopic gap
between the heads and disk......
From the above we know that the media platter from which data is
placed in binary are made from materials very different from CD and
DVD dics and there is virtually no physical contact between the
reader and media surface. Thus bad sectors though not limited to,
are more likely to be caused by abrasion of particles or irt over
the sensitive platter surface.
To ensure a proper defrag it is good to do it when the system is
free of other heavy applications and on a periodic basis. Also
computer users doing large files and downloading, p2p and stuff
will appreciate what defragging has to offer. Other than thing
everything has a working life span so make full and good use of it
with proper and correct handling should make your dollars worth the
while. 
