Unfortunately bad sectors are the enemy of every computer user in the world. A hard bad sector is a sector on a hard drive that cannot be used due to permanent damage to the surface of the disk. This is not always physical damage (although is often the case) it can be caused by the sector locking and becoming unrecoverable.
How did I get bad sectors?
What are the signs of bad sectors?
Can I repair bad sectors?
Avoiding bad sectors in the future
Courtesy : mrsupport
For Further Reading,