We’re going to describe the warning signs of a hard drive failure, explain the internal parts of a hard drive and why they fail, and then we’ll go through a few steps you can take to recover your data. While the files can’t always be recovered, there’s a chance you might be able to retrieve them.

Just remember one thing — even if your files can be restored, it will take hours of frustrating effort and might cost you quite a bit of money, too. The best way to fix a dead hard drive is to send it in under warranty and replace it with your backup drive that has all your files safely stored on it. In fact, after reading this article, you’ll find that a good back-up plan will keep you from ever experiencing the horrible feeling in the pit of your stomach when you realize that all of your files may be gone.

Why Drives Fail

A hard drive is a mechanical device with several moving parts. Magnetic platters store the data itself, while a motorized spindle spins the platters. A read/write arm moves across the platters, retrieving information or putting down new data. The arm is moved by an actuator, and the read/write heads themselves hover an infinitesimal distance above the platters. The distance is so small that a single piece of dust can get in the way.
If any of the hard drive’s mechanical parts fails, the whole drive will fail. The parts operate with incredible precision, so hard drives are rather fragile. Circuit boards, spindle motors, ball bearings — any of these parts are susceptible to failure. The worst type of failure is known as a head crash. In this case, the read/write head drops down directly onto the platter and scrapes away the magnetic material. The data in that case is totally, permanently lost. Data on unaffected parts of the platters may be recoverable, but usually data are spread around the platters, so a head crash is really bad news.
Other mechanical failures can be both a curse and a blessing. It’s a curse because it can be difficult and expensive to get replacement parts and find someone who can make the repair. It’s a blessing because, as long as the platters weren’t damaged, the data are still there. If you can get the drive running again, the data should be accessible.
The failure might be non-mechanical. Your computer uses a special index and file structure to read all the files stored on the disk. If this index becomes corrupted, the computer won’t be able to see or read the data, even though it’s still there. In many cases, this can be repaired with the proper software, although it can be tricky.
There’s one last area where a drive can fail, and it’s particularly insidious because the drive actually didn’t fail at all — the drive’s connection to your computer failed. Hard drives connect to your computer’s motherboard via a variety of interfaces, IDE, PATA and SATA being the most common. If this connection, or the circuit on the motherboard that controls the disk (called the disk controller) has failed, the symptoms can mimic the symptoms of a hard drive failure.

Signs of Hard Drive Failure

All too often, hard drives fail with no warning whatsoever. One minute the computer is working fine, the next you have a “blue screen of death” and all your data is gone. So, what’s the lesson here? Don’t rely on warning signs to predict hard drive failure. Assume that your hard drive is going to fail, and back up critical files. If you have a reliable back-up, you’ll save yourself many headaches.
Some mechanical components can fail gradually, however, so occasionally you’ll know when a drive failure is imminent. These warnings fall into two categories: sounds and performance problems.
If you spend a lot of time sitting near your computer, you’re probably familiar with the usual sounds it makes. If you hear the hard drive making any unusual noises, that’s probably a clue that something is going wrong. Grinding or screeching noises might mean the bearings or spindle motor are failing. A clicking, clunking or clanging sound could be the read/write arm slamming back and forth. Sometimes these sounds can be subtle and difficult to detect. If you think you’re hearing funny noises, open your computer’s case and listen with your ear close to the hard drive while someone else uses the computer to save or move some files.
Performance problems include a sudden increase in the frequency of freeze-ups and crashes. Of course, these types of performance problems can be symptomatic of any number of computer maladies, from viruses to memory leaks to non-drive related hardware failures. A more specific tell-tale: saving or moving files suddenly takes a very, very long time. When you run into any of these symptoms, back up anything that isn’t already saved and hope the drive lasts long enough to get everything you need copied to another disk.
For more Detail: How To Recover Lost Data from Your Hard Drive