What Causes Bad Sectors On a Hard Drive?

The hard disk is the storage device of a computer. It consists mostly of a magnetic disk and a mechanical arm that writes information to the disk. The magnetic disk is divided into smaller pieces called groups or sectors. Damaged sectors can cause information on the hard drive to corrupt or even further damage the hard drive. Modern hard drives come with extra sectors that will start to be used automatically when the originals are damaged. There are several factors that can cause damage to the sector of a hard drive.

Head reading / writing damage

The hard disk arm holds a read / write head responsible for converting electrical signals from the computer to magnetic signals stored on the disk. The head can sometimes make small errors when recording, which can render the information in a sector unusable or corrupt. The head can be damaged by dirt reaching the hard disk.

Software errors

Software sometimes makes mistakes and tells the hard drive to write unusable information to a sector of the hard drive. When the computer tries to retrieve information from that sector and can not read it, the operating system assumes that the sector has been completely unusable.

Physical damage

The disc rotates very fast while it is used, and it can be easily damaged if the head is forced to make contact with it. If the computer is pushed aggressively or if a small piece of dust enters the hard drive, the head can be hit to the fast rotating disk. Normal use can also cause gradual physical damage to the hard disk, because the heat gradually deforms the disk or the rust of the metal components of the disk.


The sectors affected by write / read errors are not physically damaged, and can easily be restored by formatting the hard disk. There are also programs designed to replace the corrupt information written to the disk, but sometimes they are difficult to use and do not always work. Physically damaged sectors can not be recovered. The computer will automatically use extra sectors if they are available. However, if you start to repeatedly receive warnings about bad sectors, you should back up the important information and replace the hard drive.

How to repair bad sectors on a hard drive?

A bad sector is a small part of a hard drive that is damaged, causing any new information from that location to be reassigned to a free sector reserved specifically for a backup. Data stored in the bad sector will be inaccessible but can still be recovered if new information is not written to it. You can try to repair the damaged sector to recover the data, although repair is not always possible.

Step 1

Click on "Start"> "My PC". Search your main hard drive, which must be assigned the letter "C: \" and be listed first in the "Hard Drives" section. You can also scan an external hard drive by selecting it. Right click on the unit and choose "Properties." Select "Tools", which is located in the tabs at the top of the "Properties" box. Click on "Check now" in the section "Checking errors". Enter your password and then click "OK". Select the "Browse and try to recover bad sectors" check box.

Step 2

Wait for the disk scan to finish. This can take a long time if you have a large hard drive. Windows will try to correct all the bad sectors it finds, but the repair may fail. You will see a report of the problems encountered once the scan finishes.

Step 3

Try to access information that was lost when the sector was damaged. Copy the files to a different location if possible to avoid losing them again.

What Causes Bad Sectors On a Hard Drive?