How A Hard Drive Works

Hard Drives contains a number of disks, called Platters, which are coated with a magnetic substance. These platters spin at high speeds under a mechanical arm called an Actuator Arm. Within the casing of your hard drive, multiple actuator arms move back and forth over the surface of each platter.

At the end of each actuator arm, called the Head, there is a small copper wire. Your computer sends a pulse through this wire which changes the state of the magnetic surface of a platter as it passes underneath. In this way the files that you store on your computer are encoded onto the magnetic substance.

Logical Data Errors

Data loss typically does not occur because of physical problems with your drive. Usually data loss occurs because the OS or hard drive have problems accessing the data at the logical level. This can occur when your computer has malicious software, such as a virus, that will purposely corrupt or damage important system files that are needed for your computer to run properly. If these viruses are not removed, they will usually continue to corrupt the OS files until the OS becomes damaged beyond repair. In this case, the original Windows XP/Vista CD/DVD would be required to re-install The operating System.

Another reason for a logical error to occur is sudden power loss to your computer. If your OS is writing files to your hard drive and your computer experiences sudden loss of power, that newly written file will appear corrupted and may not be accessed anymore by your OS. There are a few things you can do to repair the errors or corrupted sectors on the hard drive. Windows has some utilities that are built into the OS, but they are of no value if your computer will not boot up anymore.

How a hard drive stores data

New Hard Drives undergo a "low level format". The purpose of a low level format is to divide all the magnetic space on the hard drive into small "storage compartments". These storage compartments are known as Sectors. Operating Systems, such as Windows XP, group Sectors together into Clusters. A Cluster is the smallest unit of storage space that an OS will use to store data. Even if you save a very small file to your hard drive, the OS will assign it to one cluster even if it could fit onto a few sectors. When you save a very large file, it will fill up as many clusters as it takes to store the entire contents of the file.

A single file can reside in multiple clusters that are not located in the same physical location on the disk, also known as a Fragmented File. Files stored in multiple clusters that come one after the other physically on the disk are called Contiguous Files.