To gain a better understanding of the whole Hard Drive Diagnostic & Repair Process, one must first understand how hard drives operate both mechanically (physical moving parts) and logically (electromagnetic and data/software control processes) that actually write and read the data from the hard drive and interpret it into computer data files, folders and programs. The following diagrams will help to give a quick overview of how a hard drive works.

At the primary level of all hard drive operations are all the mechanical/physical parts that make up a hard drive, the Hard Drive Internal Assembly Photo (above) shows the inside of a hard drive after removing the protective cover. Each individual physical part of the drive is labeled and will correspond to similarly labeled parts in other photos/diagrams shown on this page.

The hard drive is your computer's place where the operating system (Windows), various programs (like word processors, photo editor programs, video players, etc.) and user data files (like your own word processor documents, photos, videos, songs, etc.) are stored and are accessed during the operation of your computer. The hard drive in part is similar to a "virtual filing cabinet" for storing information.

Your computer's hard drive is the single most hard physical working element of your computer and most susceptible to physical and logical break downs / faults and failures and environmental changes.
The Hard Drive Internal Parts Diagram (above) shows the parts of a hard drive all pulled apart/blown apart for further greater understanding of how it works and is assembled together. The Disk Stack Platters rotate in one direction at very high speeds of anywhere between 5400 to 10,000 RPM (Revolutions Per Minute) while the Head Actuator Arm and Head Stack Assembly moves horizontally across the Disk Stack Platters from inside to outside of the Disk Stack Platters multiple times per second.
During operation, each Head (located at the very tip of each Head Actuator Arm) on the Head Stack Assembly floats over each Hard Disk Platter with just a small cushion of air (space between Platter and Head) measuring less than the thickness of a human hair....just one small dust or smoke particle encountered on the surface of the disk platter is all it takes for hard drive catastrophic failure.
The Hard Drive Data Read & Write Operation Motion Diagram above shows how the Platters spin and the Actuator Arm moves the Heads of each of the platters to Read and Write data to the Hard Drive Platters. These moving parts, shown ion the above diagrams and photos, of the hard drive are the Physical Part of the Hard Drive Operation that can lead to physical hard drives problems and failures. Work to repair these internal moving parts in any hard drive is done in a Clean Room environment (an environmentally sealed off and controlled room where dust is almost nonexistent and exactly similar to that of a very sterile hospital surgery room and/or computer part manufacturing facility. Your computer's hard drive is, for the most part, environmentally sealed (except for a small breather hole located usually in the top cover of the hard drive) and free of most contaminants. The physical operation of the hard drive is susceptible to physical faults and hard drive failures should any particles, even as small as smoke particles and minute dust enter the internal portions of your hard drive.
Your computer's hard drive can also fail if exposed to extreme temperature and humidity changes, electrostatic discharge (like when wearing sweaters in Winter and your body putting out small sparks of electricity), and even small vibrations/movement of your computer during use.

As shown in the Hard Drive Data Read & Write Operation Motion Diagram above, the Platters spin and the Actuator Arm moves the Heads of each of the platters to Read and Write data to the Hard Drive Platters. Data is read and written via a logical process of surface electromagnetic manipulation of the Hard Drive Platters through the operation of the Heads as controlled by the Printed Circuit Board.

The Printed Circuit Board (PCB)on most hard drives is located on the outside, bottom of the hard drive assembly and also most susceptible to the outside environment of your computer's case/enclosure. 90% of most Hard Drive Failures can be directly or indirectly traced back to PCB faults and damage, many times just requiring the exact replacement of the hard drive's PCB to regain operation.
The Printed Circuit Board (shown in the top most diagrams above) contains electronic intergrated circuit chips which have functions contained within them in the form of logical/software instructions used to manipulate and operate the physical parts of the hard drive, control how data is read and written on the Hard Drive Platters, and interpret the data back into operating system (Windows), various programs (like word processors, photo editor programs, video players, etc.) and user data files, ultimately getting this information to and from the hard drive via an interface (logical/electrical connection) within your computer's motherboard, memory (RAM) and processor (CPU...i.e. Intel or AMD chip) which displays all this on your computer's screen.

The Hard Drive Data (Single Platter) Surface Detail Diagram above, shows how the the Heads of each of the Platters Read and Write data to the Hard Drive Platters, in the form of Cylinders, Tracks, Clusters and Sectors. These are the logical parts of your hard drive that dictate how data is arranged and stored on your hard drive's Platters. The Hard Drive Data (Single Platter) Surface Detail Diagram above just shows the top most hard drive Platter and how data is arranged/stored on it.

The Hard Drive Platters aseembly, layout of Sectors, Clusters, Tracks, Cylinders, positioning and movement of the Actuator Arm and Head, are all precision based down to 1/1000th of an inch. Any part being out of alignment by more than that 1/1000th of an inch can also cause various failures. Next to your Computer's CPU (Intel/AMD processor), the hard drive is the second most highly precision built component of your computer.
The average hard drive contains four disk platters (each stacked on top of the other and spaced evenly using precision made spacers on the Hard Drive Spindle. The above diagram is more of a "2 Dimensional View" of how data is stored on a hard drive, but in actuality data is really stored in more of a "3 Dimensional View" as shown in the Hard Drive (Multi Platter) Assembly Surface Data Blowup Diagram (below).
Any one file on your computer's hard drive, may either be written sequentially in a group of Sectors that make up a Cluster (where multiple Clusters make up a Track) in a particular Track (where multiple Tracks makeup a Cylinder), or the file's data may be scattered (due to hard drive fragmentation) over various Sectors, Clusters, Tracks and Cylinders, non-sequentially. Non-sequentially stored data on your hard drive takes longer to fully load/open as opposed to sequentially stored data. Through normal use of your computer, the hard drive will generally start to write more data non-sequentially over time, as various other data read and writes to the hard drive may create open Sectors (gaps) in Tracks on the hard drive Platters, this leads to what is termed Fragmentation (where files/data become scattered fragments on your computer's hard drive.
High Data Fragmentation can lead to Logical Errors where data becomes accidentally corrupted and/or mixed together with other data necessary for other files, causing hard drive Read/Write or I/O Failures. Additionally, corruptions in your computer's operating system (Windows), due to viruses and other faults, can lead to larger Logical Errors and Total Logical failures (inability to read any data from hard drive) and can further destroy data.
Based on the above details about the Physical/Mechanical operation and Logical operation of your computer's hard drive, you can guess that the Hard Drive Failure Diagnostic Process is broken down by Physical/Mechanical Failure and Logical Faults/Failures with each type of failure having further subsets of faults and failures based on the lowest levels/components involved.
The very beginning of any Hard Drive Failure/Fault diagnostic procedure, starts with you, the regular day-to-day user of the hard drive and your general observations over time including up to the time of hard drive failure. Based on what you tell us that you have observed prior to and during the hard drive failure we can start to deduce whether there is a distinct Physical/Mechanical failure, a Logical failure, or combination of the both.

Typical Hard Drive Failure Symptoms described by the owners include:

1) Noise: Clicking, grinding, squealing or combinations of
2) Heat: Hot hard drive enclosure top, bottom or sides
3) Smoke: Smoke coming from PCB or inside of drive
4) Access: Can't see hard drive listed in My Computer
5) Operation: Disk works intermittently or stops/starts
6) Errors: Errors coming up in Windows using hard drive

Just based on the above Hard Drive Failure/Fault symptoms, we can already have a pretty good idea of whether the failure was Physical/Mechanical and/or Logical. Many symptoms can be a combination of failures of multiple parts of the hard drive.
Hard Drive Failure Symptoms & Associated Hard Drive Parts
Noise: PCB board component failure
Actuator Assembly/Head Failure
DC Drive Spindle Motor Failure
(part Logical, part Physical failures)
Heat: DC Drive Spindle Motor Failure
Spindle Bearing Wear
Hard Drive Platter misalignment
(mostly Physical failures)
Smoke: PCB board component failure
Actuator Assembly/Head Failure
DC Drive Spindle Motor Failure
(part Logical, part Physical failures)
Access: PCB board component failure
Windows corruption
Data Fragmentation/Data
(mostly Logical, but some Physical failures)

PCB board component failure
Windows corruption
Actuator Assembly/Head Failure
DC Drive Spindle Motor Failure

(part Logical, part Physical failures)

Errors: Windows corruption
Data Fragmentation/Data
PCB board component failure
(mostly Logical, but very few Physical failures)
Hard Drive Failure/Fault symptoms and their related possible failing/faulty Hard Drive parts are just the beginning of the whole diagnostic process and offer a starting point for Advanced Hardware & Software based diagnostic testing as well as sub-component testing. RealTechs Data Recovery technicians will do through primary non-invasive diagnostics on the hard drive without opening it's environmentally sensitive seal to determine if more invasive, clean room procedures and work is needed and whether internal core components need repair/replacing. Ultimately it is all about getting your data back.
Increasingly on the internet there are all sorts of software, onlide help videos, and some various pieces of hardware/hand tools that claim they can repair your hard drive...BEWARE many of these so called "cheap and easy" solutions, as they either don't work or only make problems worse. The precision of construction and operation of the internal workings of any hard drive should only be worked on by skilled technicians with the proper precision tools, knowledge, and experience doing such work, in a Class 100 Clean Room facility.
Now that you are a bit more familiar with Hard Drive Failure/Fault symptoms and their related possible failing/faulty Hard Drive parts, you can start the process of getting your data back by sending in your faulty/failed hard drive to RealTechs Data Recovery for a no-cost overview/diagnosis. Please click on the PRICING section button above to start the process of getting your hard drive to us. If you still have more questions/concerns, please click on the FAQ's section button above, where you can see more information about the RealTechs Data Recover process.
Ultimately it is all about getting your treasured, irreplaceable data back in a meaningful and usable form as it was before the hard drive failure.