Hard Drives store files on fragile “Platters” within them. The information is accessed by a floating “Head”, which reads from and writes to these Platters by hovering over them on the thinnest gap of air imaginable. If the Hard Drive gets bumped somehow, the floating Head might hit the Platter and scratch it (a.k.a. A “Head Crash”). Depending on the G-Shock of the hit, the head might suffer a big enough blow that it stops floating over the Platter(s) and instead begins to scratch every part of the platter is comes in contact with. This will permanently destroy the contents of the platter (YOUR FILES) and result to permanent data loss. No software or procedure will be able to restore data that has been destroyed in this manner.
This is why IT’S KEY to bring your malfunctioning hard drive to a specialist from the start, so that they can inspect it in a real Certified Lab (Clean-Room or Glove-Box) in order to prevent further damage to its precious platter(s). Running software on the Drive without inspecting its internal condition first will probably damage the Platters, making it almost impossible for even a specialist to recover anything.
A Hard Disk Drive read/write Head hovers above its Platter`s surface at a distance that is 5,000 times smaller than the diameter of a human hair. It has been said that the read/write Head flying over the (Disk) Platter surface is like trying to fly a Jet plane six inches above the Earth’s surface.
More Useful Basic Knowledge:
1, Hard drives record data by magnetizing ferromagnetic material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material.
2, The platters are spun at very high speeds. Information is written to a platter as it rotates past devices called read-and-write heads that operate very close (tens of nanometers in new drives) over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it.
3, Modern drives also make extensive use of Error Correcting Codes (ECCs), particularly Reed–Solomon error correction. These techniques store extra bits for each block of data that are determined by mathematical formulas. The extra bits allow many errors to be fixed. While these extra bits take up space on the hard drive, they allow higher recording densities to be employed, resulting in much larger storage capacity for user data.