Hard Disk Bad Sectors.

The most common occuring problem among hard disk drives is bad sector occurence. There are two types of bad sectors: logical and physical.
While logical bad sectors can easily fixed using particular software, physical bad sectors can be irreparable. But it doesn't mean there is absolutely no hope, there is still a chance to recover the bad sectors depending on how "deep" the bad sectors are. So, below I am going to consider only physical bad sectors, their symptoms, reasons for appearing, types and ways for possible maintenance.
There are mainly two symptoms you can come across with:
1. Blue screen of death appears often showing the error code indicating that a memory read attempt failed. It follows with inevitable restarting and the next blue screen follows pretty soon with similar error code again. The same message is displayed when there is a problem with DDR memory. But memory modules are easily replaced, or even repaired by replacing the bad chip.

2. Operating system doesn't boot with a message showing that some system files can't be found.
One of the reasons for bad sectors is that some areas of HDD, which are most often used, "wear out" and become harder to read and finally, completely inaccessible. Though it is possible to "recover" these sectors using some applications, it is better to get a new HDD for usage as the main system drive and the repaired one use for other purposes. The reason is that even though the bad sector is fixed, all your data is safe and the HDD is working again, there is a risk that the previous or the next sectors are also about to crash soon. Using for additional storage purposes is not the worst choice for such hard drive.

Another reason for physical bad sectors is a shock, which exceeds the acceptable limits, especially, inflicted while the HDD is operating. In this case numerous bad sectors are almost unavoidable. Usually, after such an accident HDD comes to an absolutely useless condition, when it will keep making a specific sound trying to start spinning, but never will. Imagine a disk rotating with the velocity of over 5000 rpm. Is it possible to make a single dot on it by touching it with, let's say a pencil? The answer is "No". It is absolutely impossible to avoid a nice clear circle instead of a dot. For an HDD such a circle means a huge area of storage, which is inaccessible.
Nowadays, the HDDs have average size of 500 GB and the price ranges around $70. This is an affordable price, but the information contained in HDD might be more expensive. So, such problems as described above need some solutions, and favorably with positive results. As I mentioned, depending on the situation you are, you can use software, which in most cases are helpful. These kinds of applications are able to access the drive regardless the file system and recover the data and even the bad sectors. If you are not sure or it seems that the HDD is completely dead, probably, it is better to have the job done by a professional.

Article Source:-http://hd-data-recovery.blogspot.com