First of all we must understand what an error is and how errors can appears. The misapprehension between the data and between the boards and the compatibility of them can result in an error. All of the errors are supported by the hard disk and can be very destructive to it.
To make it easy for all of to understand what a bad sector is we will try to explain it away from the technical terms. Consider you have a piece of paper and the entire paper is the writable zone where your hard disk saves information. On this piece of paper we draw lines to divide it in small squares. One small square represents a sector of your hard disk, and if we divide one square in to 4 squares we can obtain, imaginary of course, 4 cluster. Ok know you want to write a sentence on the paper. You will notice that there no room to write the sentence in only one small square and you will need a certain amount of squares from different portions of the paper; know write down your sentence.
After that take scissor and cut a word from the sentence in the middle of it. You as a person can still read the sentence because we can realize what word is messing from the sentence but a computer to show you that sentence needs all of the words to reproduce it for you. The part that you cut from the sentence is our bad block, and now you can understand how the hard disk functions. And all of you know that on the driver is more then a sentence written, and that it contains millions of letters and numbers and also holds information about all of the boards, along whit their drivers, that are in your personal computer.
Some surface errors have connections whit the hardware equipment of the computer directly and can create physically bad sectors on the hard drive, and that means a cluster from the hard disk sector is unreadable. The writing action on the hard disk is possible thanks to a “writing head” that floats at a distance of 0.3 microns over the writable layer of the disk. If one or more heads actually touch the writable disk the chance to destroy that cluster is almost 100%.
The bad sectors are in definition a portion of the hard disk writable part that can not be change (read or write). So because of this definition the data that are on the bad sectors may be lost forever.
You can be easily be trick to think that your hard disk have bad sectors, most of the time are errors that appear because of the over churching of the partition or of the Windows directory.
Bad sectors also known as simple as “bad” can appear to any hard disk after a time of function. In most of the cases the bad sectors that appear are not in a bigger quantity from your stocking space (about 0.01% for newer hard disk). For the new gene ration of hard disk there are some spare clusters just for these problems. When a bad sector appears the safety measure remove the information that it contains to a spear cluster and that way avoids the lost of data or the corruption of the data.
In a generally idea a bad sector is a big problem for your hard disk and for your entire computer. There are some programs that can repair them if there are not physically and are from data corruption but that is another story about the hard disks.