The first step is to determine if it really is hard drive failure you are experiencing. Did you install any new hardware since your last successful boot-up? If so, unplug those devices and try to re-boot.
No go? OK, if you're running Windows, try to start up in Safe Mode. Reboot your PC, and hit the F8 key when the computer is starting up. Choose the option to go into Safe Mode. If you can get to the Windows' login-screen, you are probably having a software problem, not hard drive failure. You can do a re-install of Windows to get to your files (see Recovery Console) or you can use Windows' System Restore feature to get your PC up and running again.
In some cases a damaged master boot record or partition table can render a disk unbootable, but all the data is still intact. See Fix MBR for some help with that relatively simple repair job. In one case, my hard drive got totally mucked up, and neither the FIXMBR nor FIXBOOT commands could restore the drive to working order. But I found a wonderful program called TESTDISK that was able to analyze the disk and recreate both the partition table and the boot record. I was certain that all the data was lost, but TESTDISK did the job for me.
Check Under The Hood
What if you can't get into Safe Mode? There are still a couple of options available. Unplug everything (the power plug and ALL the cables) from the computer. Now pop open your computer's system unit and try to reseat the hard drive. It might look scary at first, but there's nothing inside a computer that will bite you. Take a look at the pictures in my article Add a Second Hard Drive to familiarize yourself with the components you'll be looking for -- the hard drive, the motherboard connectors (IDE or SATA) and the cables that connect the hard drive to the motherboard.
Unplug and reseat the all the cables that plug into the hard drive, then follow the cable to the motherboard and reseat that end as well. It's possible that the cable was just loose, and your drive will work fine after this simple procedure. You can also try swapping the IDE or SATA slot that the drive plugs into. Look for connectors on the motherboard labelled IDE1 and IDE2, or SATA0 and SATA1. Move the cable from one plug to the other, restart the system and hope for the best. If all the above options fail you can assume your computer wasn't lying, the hard drive is faulty. There are methods available to try and get your data back.
Hard Drive Data Recovery
The practice of retrieving data from damaged or inoperable disk drives is known as data recovery. Data recovery experts have a thriving business. Just like a car, a computer can break down and parts wear out. Hard drives are no exception. Because of this potential for failure, backing up crucial data to an external source other than your hard drive is essential. (For backup help, see Backup Up Your Files.) For now, let's assume you have hard drive failure with no backups of your files, and focus on what you can do to recover your data.
There are programs available online that can be downloaded to aid in data recovery. One program is Inspector File Recovery, which will help to recover Windows files. The program is free, however you do need to have a secondary hard drive installed with a Windows OS on it. Installation is user-friendly, and after install the program will prompt you through several data reconstruction options. Another program is TOKIWA's Data Recovery. With Tokiwa's program, you do not need the secondary hard drive; you can download the program to a USB drive or a floppy disk and run it on the PC that the unreadable drive is attached to. ProSoft's website offers Data Rescue II, an application available for download for free trial to recover Mac files. RTT's website has a free program called R-Linux, that will recover Linux and some versions of UNIX files.
There are also a range of web-based data recovery sites that you can access (from a working, Internet-connected PC, that is). These are remote data recovery sites. OnTrack is one site that provides this service. They offer remote web-based recovery that will scan your failing drive and try to recover lost data. Another data recovery company is Web Recover, which will attempt to recover your data through a web browser.
Data Recovery Services
Bear in mind, whether you use the downloadable recovery programs, or the web-based ones, there are no guarantees that your data can be reclaimed. The above programs and services will be able to recover your data, provided your hard drive problem is not a purely mechanical one. Often, drive failure error messages stem from a bad sector or failing partition on the drive. If data recovery programs aren't working for you, and in addition, you are hearing any strange noises coming from the drive (see Hard Drive Makes a Clicking Sound), or if BIOS cannot recognize the drive, then you are looking at mechanical disk drive failure. If it's imperative that you retrieve data from a drive that is physically damaged, there is still hope. OnTrack and other data recovery companies give you the option of sending the damaged drive to their engineers who will evaluate your hard disk, extract a file listing from it, and will retrieve any data possible. This type of service ain't cheap, though. The standard evaluation cost is US$100. Afterwards, the actual data recovery fee can run anywhere from $500 to $2500 depending on the amount of data and labor involved.
Just remember, a "hard drive failure" error message does not necessarily mean all is lost. You have a range of tips, tools and techniques that may bring the drive back to life, or at least help you recover some of your important data.
Answered By: DanielTWD - 9/6/2007