Update: scroll down to comment #10 for a better picture of this hard drive. Feel free to copy and use the picture.
“Can you get my files back?”
“No.”
Inside your desktop computer is a data-storage device called a “hard drive”, so named because it stores data on a spinning aluminum platter (as contrasted with the mylar data-storage surface of a “floppy disk”). These platters spin 60 times per second or faster and are mirror-shiny, perfectly flat as a telescope mirror is perfectly curved. They are usually electroplated with a cobalt alloy because aluminum cannot record magnetic impulses.
The data is written onto the platter by a tiny electromagnet that floats a couple millionths of an inch above the platter at the end of a head actuator, which positions the head above the precise location of the magnetic imprints. This electromagnet is called a “Read/Write head”. Normally it never touches the platter when the drive is turning.
When drives fail, they usually make a clicking noise known as the “Click Of Death” as the drive controller (the circuit that steers the actuator arm) seeks but cannot find track zero. Another failure mode is a “Drive Crash”, where the head literally crashes into the moving platter, grinding away the surface (and your data).
This drive made a horrible screeching noise in operation as the R/W head ground its way into the aluminum. Usually the platter surface is intact except for the inner-most track (track “0”), but in this drive there was a bonus; the head kept seeking after the crash occurred, grinding up the whole surface of the disk. The drive was full of aluminum powder.
Notes:
By the way, if you can get ahold of an old hard drive, take it apart. They’re very interesting devices. The platters are so perfect you can reflect a visible spot of sunlight a couple blocks away. Hard drives contain the strongest magnets most people will ever see – usually a neodymium alloy with cobalt, iron, and/or samarium. (and strong enough to stick a magazine to your refrigerator). The ring-shaped spacers between stacked platters are (like the platters themselves) machined to absurdly fine tolerances – for some reason it is inspiring to handle such precise parts.
Shown in this picture is the interior of a normal hard drive. Upper-center is the data storage platter, which rotates around the main spindle. Extending into the platter area from the lower right is the actuator arm. At the upper tip of the arm is the read-write head. At lower-right is the “voice-coil” portion of the actuator (where the super-strong magnets are located), which moves the arm around the actuator spindle to locate the read-write head on the platter surface. Not shown is the drive motor and control circuit, as they are on the other side of the drive.