When people experience the symptoms of a malfunction of the data storage media often try to put a remedy "DIY" underestimating the risk of further damage the memory device.
To answer the question “what to do?”, in case of malfunction of the hard disk, is therefore appropriate to note briefly what are the main symptoms that characterize an impending, or already occurred, hard disk failure, and what are the main types of damage underlying the manifestation of symptoms.

What then are the typical symptoms of hard drive malfunction?
What can happen inside a hard drive when you discover these symptoms?

• Symptoms:
  • The hard drive sounds a strange and continuous ticking
  • The hard drive emits a strange noise
  • The hard drive emits a screech
  • The hard drive emits smoke or burning smell
  • The hard drive is no longer detected by BIOS and / or operating system
  • The system can no longer boot properly
  • The system stops suddenly at work
  • The hard drive is detected by the BIOS with a strange name
  • The hard drive is detected with an unusual capacity
• Types of faults:
  • Logical faults:
    
    •  These are problems that arise from malfunction of the storage device, the inability of the operating system to access, through the mechanism designated to storage and organize files within the media (file system), to a portion of data, or to operating areas of itself:
      
      • User errors:
        
        •  Occurs when the user does not follow the correct procedures, as in the case of disconnecting from a computer USB support without going through the safe removal procedure.
      • Sudden system crashes:
        
        •  Occurs, in these cases, without intent by the user, for example, due to a blackout room, where the computer (or the storage device) is not connected to a UPS
      • Voluntary or involuntary actions:
        
        • Deletion of files and folders
        
        
        •  Formatting of storage media containing important data on which it has not been, previously, made a back up
      • Sabotage, espionage:
        
        •  In some cases, the file system corruption, formatting and deletions may be the result of certain actions premeditated and carried out by third parties who have an interest in creating chaos, disorder, damage, to gain competitive advantages in its "adversary" or to carry out an extreme form of protest.
      • Computer viruses:
        
        •  The file system corruption, it could also be the result of activities of viruses which, settled into the computer, modify, overwrite, portions of the file system essential for booting the system.
  • Firmware corruption:
    • If we wanted to make a comparison with computers, the firmware would be the bios of the storage medium. It is software that enables the storage medium to interact with your computer. It is often integrated into the pcb in ROM or flash memory, although for some models is partially printed in the system sectors portion of the platters, making the storage support unique and not working if disassembled in its macro components. That is why, in these cases, the replacement of damaged pcb with an equal working one, has no effects for the repair and data recovery.
      The firmware provides all the parameters of communication and is essential for the functioning of the drives, and its corruption prevents the read / write data processes. It stores its information in specific areas which are accessible only through its own infrastructure.
      Inside the firmware are a lot of essential information to the operation of the hard disk, including the smart calibration modules, tables of defects, and the translator of the service.
  • Physical failures:
    • Mechanical failures:
      • Platters rotational motor failure:
        • The high rotation speed given to the platters placed the technical before big challenges to solve the problem of vibration and heat generation.
          Despite improvements, the rotating shaft of the engine may freeze due to the wear of bearings or to the exit from the axis rotation center. It can happen that, due to ordinary or un-ordinary stress, can damage the motor rotation axis, making unstable the system platters-heads.
          This is usually the fault of exogenous, due to external shocks (shocks, falls, etc.). But, rarely, may also occur due to manufacturing defects or wear problems due to prolonged use of the hard disk.
      • Read/write heads Failure:
        • The head is a mobile component responsible for reading and writing the magnetic layer that cover platters.
          When data passes under the area of influence of the head, due to magneto effect, bits can be written or recorded in the magnetic surface of the platter. Therefore, the interaction between head and magnetic layer is not physical but magnetic. In fact, the head never touches the platter physically, using the airflow created by the same rotation of platters, lifts and flies over the surface at a microscopic distance. The contact between the head and the platter will damage the magnetic surface locally and the data stored in it. However, the contact may damage the head itself, making the data completely inaccessible.
          Also, some hard drives have a sort of airstrip where the heads land before the disk stops. This ramp, some times, by heat or mechanical stress, misaligned and may determine, upon arrival of the head, its destruction.
      • Voice coil motor failure:
        • Heads are mounted on an arm that is driven in linear translation along a shaft from a particular engine that implements an interaction between a permanent magnet and a coil which in turn generates a magnetic field.
          Due to improper wear or stress, it may happen that the axis of rotation of the actuator is misaligned or stroke limiting or not allowing the linear movement of the arm.
          Therefore the heads, which are perfectly aligned with the platters, not only may no longer be able to read magnetic tracks but can also dangerously close to platters, damaging them.
      • Damage due to contact with the platters:
        • The excessive approach of the magnetic heads to the platters surface, due to the heat from the device or to a mechanical action from outside, and the consequent alteration (scratches and scuffs) of magnetic surface as a result of the contact, shall be technically called "Head Crash".
          Il danneggiamento delle unità logiche a cui accede il file system o il sistema operativo, in questo caso, non consente l'avvio del computer o, in fase operativa, ne provoca il blocco improvviso. The corruption of the logical drives used by the file system or by the o.s., in this case, does not allow the computer starts or, during operation, causes its sudden block.
    • Magnetic faults:
      • Magnetic corruption of the platters:
        • The instability of the magnetic layer, which is coated the surface of the platters, can affect logical sectors on the hd.
          The corruption of the logical settors accessed by the file system, in this case, does not allow the computer starts or during operation, causes the sudden block.
      • Magnetic corruption of voice coil motor:
        • The voice coil is a special type of motor that uses the magnetic properties of materials to determine the movement of read / write heads.
          The magnets corruption make it impossible to wear normal function of the hard disk, because platters would no longer be written / read in accordance with the procedures modulated within the firmware.
      • Corruption of magnetic heads:
        • Heads are made from layers of magneto-resistive material that, losing the magnetic properties, causes the fail of head ability to read and write the magnetic layer of platters.
          In this case it is necessary to replace them.
    • Electronic failures:
      • Are problems associated with damage to electronic components of the hdd which may arise due to fluctuations in supply voltage, or to the high working temperature of the hard disk. The electronic component, like the others, is essential in the operation of any storage medium, enabling access to data.
      • PCB corruption:
        • Power surge due to an inadequate or damaged power system are the most common cause of this type of damage, burning components on the board.
      • Coils of the rotational motor of the platters:
        • The heat inside the engine, because of increasing speed required by modern hard drives as well because of crash of the engine, can cause burning of the motor windings of rotating platters.
          In these cases it is necessary a motor replacement.
      • Voice coil motor windings:
        • Voice coil motor windings, interacting with a permanent magnet, implement the movement of heads for reading / writing.
          When electrical damage arise, the control by the electronic control system places on the board becomes impossible.
      • Preamplifier corruption:
        • Signals flowing between the magnets placed on the head and the control circuit are very weak and are amplified immediately after their detection by a circuit inside the hard disk.
          Excessive heat and continuous movements, can erode and damage the circuit making it impossible the correct communication between the two subsystems.
• What to do:
  • Preventive actions:
    • Perform Backup Frequently:
      •  It is always necessary when you work with your important files, to make backup copies. Losing data and arrange for the subsequent recovery always involves a very high stress and produces a distraction from the goals that we set itself for the realization of a job.
        The uncertainty about the type of damage suffered by the storage medium on recovery times, and on the costs, the cost and discomfort to be incurred will certainly disproportionate to the commitment required to implement a more secure and steady Storage system on CD, DVD, other hard drive, internal or external, networked machines, or external servers.
        Use back-up programs, even free, like SyncToy, SelfImage, DriveImage XML, Cobian Backup, etc.. , is always the best policy for any person who gives value to their work.
    • Making a plan and structuring of the system:
      •  A 'very important preventive action is to install the operating system on a hard drive and data on one or more separate media. This technique is the best for data management in comparison to a all-in-one large hard drive solution.
    • System maintenance:
      •  Check frequently the level of fragmentation of data in the hard disk and, if high, proceed to defrag. For the long time required to do it, especially on large capacity media, run this type of operation at night or on weekends.
    • Installation of an electrical protection system:
      •  To prevent your hard drive is subject to the risk of blackouts or power surges, you should connect your computer and external media to adequate UPS that keep a constant and steady supply.
  • After the first symptoms:
    • If the harmful event has already occurred, unfortunately, one thing is certain: every action attempted, either physically or through the use of downloaded software without adequate facilities and expertise for the recovery could lead to deterioration or even undermine every chance of recovering the data.
      In general, and on the upon highlighted awareness of responsibility, the steps are:
      • Detection and recognition of the problem:
        •  Note the symptoms (hd un-detection by the operating system, inability to start the pc, noise from the support, smell burning, etc.), and the cause that created them (disconnecting USB support without running the safe removal procedure, power supply black out, dropped support, etc.)..
      • Verifica dei collegamenti:
        •  Make sure that every connection is correctly done and possibly try using different hard drive connection cables.
      • Re-configuration of hard disk:
        •  Try to connect HD as slave or secondary master on a different computer than the one the problem occurred in.
      • If it still does not work:
        •  If yet the hard disk is not working, stop here. Unplug your support and call us immediately.
          Do not further attempt at recovery (disc opening, card replacement, etc.).. Depending on the type of damage that has occurred, every attempt would definitely affect the recovery of data, or exponentially increase the costs of recovery. Also, do not use data recovery software. Again force the disk without knowing what really happened inside the support, could cause irreparable damage, to the destruction of the disc and the permanent loss of data.