A hard disk drive consists of a mechanical part (HDA) head-and-disk assembly and a (PCB) - printed circuit board. HDA acts as a case for all mechanical parts of a drive and contains one more chip performing the functions of a preamplifier/commutator. The PCB consists of series of chips which control the mechanical parts, encode/decode data on the platters/magnetic surfaces, then transfer the data through an external interface. Generally, PCBs are located outside HDA, in its lower part. In certain hard disk drives, such as the Seagate-Barracuda series, the controller has an additional metal cover protecting the electronic components from damage.

    Hard disks drives, reportedly, have "Mean Time Between Failures" (MTBF) of 500,000 to 1,000,000 hours. It is claimed that "on average, that a drive fails after the specified number of hours, with half of the drives lasting more than that and half lasting less. 500,000 hours is about 57 years. Clearly, not all drives last 57 years". However no data recovery specialist can endorse such claim.

    The Hard drive can spin at a rate varying from 3,600 rpm to 7,500 rpm.

    As a single speck of dust entering a hard disk could cause fatal results. It is larger than the distance between the read/write heads and the platter in a hard disk (40 microns, a human hair being 100 microns thick) and its collision with the Hard Disk head would have detrimental consequences. Therefore, a single molecule of dust or bacterium could impede any recovery.