How To Recover Lost Data from Your Hard Drive

Here you can see the mechanical parts inside a hard drive. The platters are visible along with the spindle they rotate around. You can also see the actuator mechanism and the read/write arm.
Here you can see the mechanical parts inside a hard drive. The platters are visible along with the spindle they rotate around. You can also see the actuator mechanism and the read/write arm.

Hard drives fail. It's a fact of life for anyone who uses a computer. If you store irreplaceable information on your hard drive, then a failure can be a catastrophe. But can you recover the family photos, work documents or financial data that you kept meaning to back up, but never did? There might be hope, so don't give up on that broken hard drive yet.

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

The read/write head floats just above the platter surface. A piece of dust or even a fingerprint can cause a head crash.
The read/write head floats just above the platter surface. A piece of dust or even a fingerprint can cause a head crash.

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.

The next section will describe the warning signs of impending 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.

Next, we'll troubleshoot your dead drive.

Troubleshooting a Dead Drive

An improperly aligned IDE connection can prevent a drive from being detected by the BIOS, but this is easily fixed.
An improperly aligned IDE connection can prevent a drive from being detected by the BIOS, but this is easily fixed.

When your drive seems to have given up the ghost, there are some steps you can take to determine where the problem lies. If your computer is running Windows, the first thing you should do is reboot the computer and go into the basic input/output system (BIOS). Usually you do this by pressing the Delete key during the boot-up sequence -- watch for on-screen prompts. BIOS has a utility that autodetects drives. Run this and see if the drive shows up. If it doesn't, there may be a problem with the connections between the drive and the motherboard. Check all those connections.

If the drive does show up, then you can run some more diagnostic tests. You'll need another functional computer to accomplish most of these, unless you've planned ahead. Find the model number and manufacturer of your hard drive. Go to the manufacturer's Web site and look for the company's proprietary diagnostic software. You'll have to download and then burn it to a CD-ROM or save it to a floppy disk, depending on what the "dead" computer is equipped with. Boot the dead computer from the diagnostic disk and run it. The diagnostics should give you some indication of what the problem is, although sometimes it will find no problems, even though the drive is still not working.

You can also create a bootable virus scan disk and scan the dead drive for any viruses that might be causing the problem. If your computer is infected, you may be able to use the virus scan disk to repair the problem as well.

If all has gone well, at this point you should have a rough diagnosis. You might not know exactly what's wrong, but at least you've ruled some things out and narrowed it down. But what if none of those troubleshooting steps worked? Try connecting the drive to another computer, one that you know works. This will let you know if the problem is really with the drive itself.

Also, open your computer's case and listen closely to the drive when you boot up the computer. Is it totally silent? That means the platters aren't "spinning up," indicating a serious mechanical problem. Does it make any of the warning sounds we mentioned earlier? Remember, these are also a sign of mechanical failure. If it sounds perfectly normal (generally, a steady hiss as the platters spin and internal cooling fans activate -- although different drives make different sounds), then the problem is probably not mechanical.

In the next section, we'll explore some different ways to repair a hard drive.

Hard Drive Repair

If you've determined that your drive has a mechanical problem, you may have some difficulties to overcome. The drive might be fixable and your data recoverable, but it might require a professional repair, which can cost hundreds or even thousands of dollars. The main reason for this is that work on the internals of a hard drive have to be done in a "clean room" environment. Any piece of dust on the platters can ruin the drive.

You could attempt a mechanical repair on your own, but you'll need to find exact replacement parts from the exact model and version of the drive. This can be a huge challenge all by itself (even for professional data recovery experts). You might be able to replace a dead circuit board yourself, but spindle motors and read/write actuators are very difficult to deal with. Also note that opening your hard drive's case will void its warranty. If you do decide to go this route, remember to never touch the platters themselves. The oils from your fingertips are enough to ruin the drive.

A problem with a corrupt file structure or disk index is solved with special software. There are some utilities, such as fdisk, built into most operating systems that can be used for this purpose, but you have to be very careful. Changing the partitions in the drive or formatting it might solve the problem, but you'll lose all your data. Another option is to use a specialized recovery utility such as Disk Warrior to repair the problem while keeping as much of your data as possible. Some corrupted files may not be recoverable.

Up next, a look at some extreme forms of hard drive repair.

Extreme Hard Drive Repair

There are some rather odd hard drive repair suggestions floating around the Internet. Enough people claim that they work that they're worth a look in dire circumstances. If your drive seems to have a mechanical problem or simply a problem you haven't been able to solve, and you're unwilling or unable to get professional data recovery, you might have one last ditch shot at retrieving your data.

Before you try any of these techniques, make sure you're ready to immediately recover your data. The easiest way is to have the connections ready to reconnect the dead drive to a computer with either a DVD burner or a large flash drive to move your critical files to. Also, please remember that these methods may not work and may even cause additional damage to your hard drive. If you have any questions about what you're doing, it's probably best to have a professional look at your hard drive for you.

Sometimes the mechanical parts within a hard drive can get bound up or jammed. A sharp physical shock might free things up long enough to get your data. Keep in mind this is the exact opposite of how you should normally treat a hard drive, so this is really a last resort. First, try whacking the side of the drive with the handle of a screwdriver or a small mallet. If that doesn't help, try the drop method: Hold the drive about 6 inches (15.2 centimeters) above a hard surface and let it fall (make sure the metal chassis is the part it lands on). You might have luck with successive drops from slightly higher up.

The most unusual method of hard drive repair requires you to freeze the drive. The cold temperature shrinks certain metal parts and can free up jams or binds. Put the drive in a sealed plastic bag and then put it in the freezer. Reports vary from a minimum of two hours to 24. If you have nothing else to lose, it's worth a try.

There are some even more extreme forms of hard drive repair, but they can only be accomplished by professionals. Some of these techniques can recover data from drives that have been burned and melted in fires or damaged by water. Even drives that were submerged in floods can have recoverable data on them. The methods involve recovering the platters and using new mechanical parts to read whatever magnetic data is still on them. This absolutely has to be done in a clean room, so there's really no way to do it in your own home. It's expensive, but if you absolutely need that information, it may be worth it to you.

For more information on hard drives and related technologies, spin over to the next page.

Related HowStuffWorks Articles


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  • Data Recovery Pros. "Data Recovery From a Failed Hard Drive - Freezing Method." (May 14, 2009)
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