Dropping a hard disk drive could have disastrous effects, but it is important that you do no panic should this happen. Under no circumstances should you power up the drive again. The delicate nature of hard disk drives which are built to high tolerances are vulnerable should they be subject physical impacts with even a slight knock capable of causing serious damage.
Following impact damage the act of powering up a drive could result in any damage causing further failures of the hard disk. It is therefore important to contact a professional data recovery company with the relevant expertise and knowledge who can advise you how to proceed. If you send a hard drive which has suffered an impact event, it is important to state that information, as it ensures the engineers are fully aware of the potential problems with the drive.
Damage to the Hard Drive
Impact damage typically causes two possible failures to occur, even when the drive is not operational. The result of this may be a failure of the spindle motor or the read/write heads or in the worst case both may occur at the same time. If the drive is powered on when either of these failures has occurred, it could lead to the eventual loss of all data.
If the read/write heads are damaged their alignment will almost certainly be outside the normal tolerances. At best this will result in the drive not being able to read any data from the platters. In most cases however this will likely cause them to impact with the platters if power is applied to the drive damaging the recording surface.
Spindle motor failure may cause an alignment problem or cause the platters to vibrate due to resonance. Both of these are likely to lead to the read/write heads being brought into contact with the platters. Any impact with the platters by the read/write heads will result in debris which is likely to compound the problems even further.
Dropped Hard Disk Drive Recovery
Should your hard disk drive suffer an impact event the drive must not be powered back on as it may result in severe damage. Such an event could be something as simple as hitting your laptop or knocking an external hard disk over. Hard drives in this state must only be opened in a clean environment, by qualified personnel such as a data recovery specialist. They will rebuild the hard disk drive in order that all the data can be recovered.
It important to understand that even when the drive is not subsequently powered up, that surface damage to the platters could still be present, particularly if the drive was operational when the drive was dropped. Recovery rates for hard disk drive which have been dropped are high, but any attempts to recover the data yourself will reduce the likelihood of success.