This is a work-in-progress.
This guide is intended for the Windows operating system, and the methods found here may or may not work with other operating systems. For the time being, it will be assumed that DESKTOP systems are involved, until I can add more info for dealing with laptops. This guide is NOT intended to help with physical hard drive failures, or accidental file deletion/formatting/partitioning issues. That's a Guide for a different day 
Also, if your hard drive seems to be making new, unusual noises, it may be about to physically fail. You should turn the system off and seek help from a qualified professional under these circumstances.
Here's a typical posting seen here in the computer forum:
HELP!!! My computer was working fine, but the next time I tried to turn it on, I couldn't get into Windows! How do I get my files back?
First of all, don't panic. Unless you've had a catastrophic, physical hard disk failure, the odds of getting all of your files back are actually quite good! Worry about recovering your data FIRST, then worry about fixing your computer LAST.
The number one rule is: KNOW WHEN TO HIRE A PROFESSIONAL!
If you are at risk of losing data that you absolutely cannot live without, you should, without a doubt, hire a professional company with an excellent record of recovering data in even the most difficult of circumstances. One such company is Ontrack. They are considered by many to be the best in the data recovery industry. They routinely recover data from drives that have been in fires, floods, and other dire circumstances, including intentional sabotage. They are expensive, but this is the price you pay when you don't take the time to backup your files!
The number two rule is: "DON'T DO ANYTHING STUPID!"
Slow down, take a deep breath, and work on this in a logical manner, because these techniques, if not followed correctly, may actually result in making your problem worse! If you do not already have some experience working inside of computers, and installing and configuring of hard drives, you, too, should strongly consider finding a professional computer technician that has the knowledge and proper tools to recover your data!
This is a good time to mention that, should you follow the advice given here, you will be doing so at your own risk. I (nor anyone else) shall be held accountable for any problems that arise from following this guide, or other advice given. Period.
With that said:
The majority of computer failures that leave data inaccessible, in my experience, have nothing to do with a genuine hard drive failure. More often than not, you can't access your files because something like your power supply has failed, or there is corruption to a file that's needed for your system to boot properly. Fix these problems, or work around them, and you'll find it very easy, most times, to recover your data at nominal costs.
Let's take a common scenario:
You're using your computer as a thunderstorm is approaching. Before you can shut the computer down, your home and your computer lose electrical power. When the power comes back on, you try to boot your computer, but find there is now a corrupted file in the system registry, and you can no longer boot fully into Windows. Your stomach sinks as you realize you have 5 years worth of digital photographs on your computer, and have never made a backup!
The good news is that your data can almost certainly be recovered!
Now, let's explore a few common ways of recovering your files:
Method ONE:
I call this the "drive as slave" method.
Cost: Usually FREE.
Difficulty: "Easy" for experienced persons, "difficult" for inexperienced persons, You will need a second, working desktop computer available.
In this method, our intention is to simply remove the "bad" drive from the dead system, and place it in a working system long enough to recover the data off of the drive.
Begin by unplugging the computer! Follow your computer's manual to open the broken computer's case. There's usually only a few screws that will need to be removed. Once the case is open, locate the system's main hard drive (most systems will have only ONE). The hard drive is usually the drive located lowest inside the system, beneath the optical drives (CD and/or DVD drive). In the standard system, there will be two-to-four screws that hold the drive in place. First you will have to carefully remove the data and power cables from the drive. You may need to consult your PC's manual to figure out how to physically pull the drive out of the system.
After the drive is removed from the broken system, you will need to read the label or wording on the hard drive for instructions on how to set it as a "slave" drive. Usually this requires that only one small "jumper" be moved to a different set of pins. This usually takes only seconds to do, but you may need a pair of tweezers to carefully grasp the jumper.
Once the drive is set as "slave", you will need to unplug your other, working system's power cable, and prepare to place the "bad" drive inside of it. It is usually not necessary to permanently mount the "bad" drive in the good system, as file recovery usually takes a short amount of time. Ideally, you will add the bad drive to an open connector on the same cable as the good drive in the good system. You will then have both the good and bad drives on the same cable, in the working system. If there is not a second connector available on the cable, you may need to go buy an IDE cable with more connectors, or see if your other system has a cable with more connections. An alternative is to remove an optical drive from its cable, and attach that cable to your "bad" hard drive.
Once this is done, you should be able to plug the system back in and boot it up. Most computers will now recognize that you have added another hard drive, and boot with no problems, so long as the hard drives are jumpered properly.
EDIT: Here is a web page showing a hard drive inside of a system, and explains jumpering the drive, adding it a "slave", etc. Sometimes a few pictures say a 1000 words!
Once you get the computer booted, open "windows explorer", look for your "bad" hard drive, and proceed to copy your files from it, most likely onto your "good" hard drive, space permitting. Here are typical locations that you'll find your files at with Windows 2000 and Windows XP. Once your data is recovered, shut down the good computer (unplug it), remove the "bad" drive, close the case, plug it back in and it should reboot just fine again.
Now you can change the jumper on your "bad" drive back to its original setting, and place it back in the dead system.
Now you can post to the forum and ask how to fix it.
EDIT: Method ONE will work with LAPTOP hard drives as well, IF you purchase a Laptop to IDE adapter, for about $20 at a bricks & mortar store. This will let you temporarily place your laptop hard disk inside of your desktop system. This web page has an example of what you'll need.
Method TWO:
I call this the "external enclosure method".
Costs: You'll need to purchase an external enclosure if you don't already have one. You should be able to find a decent one for under $50. Read the "Enclosure Guide" for more information.
Difficulty: This is probably the easiest of the methods you'll find here.
In this method, the intention is to simply remove the "bad" drive from the dead system, place it into an external enclosure (following the instructions from the manufacturer), and then plug it into the USB port of a working computer (for best results the working computer should be running the same version of Windows, or better, than the dead system was running. This is because old operating systems cannot read new file systems.
Once you plug the external enclosure into a working system, open windows explorer, find the hard drive that holds your files, and copy them to the working system's hard drive, space permitting, or burn CDs/DVDs as needed.
Once your data is recovered, remove the hard drive from the enclosure, place it back into the dead system, and then make a post asking for help fixing your system.
EDIT: This method works for laptops, too, IF you purchase an enclosure MADE FOR LAPTOP hard drives! Pleas read your laptop's manual for information on removing your laptop's hard drive properly.
EDIT: Some newer hard disks are known as "SATA" drives. They require different connectors, and therefore different enclosures. You may want to CAREFULLY take the hard drive with you to the store (in an anti-static bag) for a knowledgeable employee to identify the drive and suggest the proper type of enclosure for it!
EDIT: There are also "USB to IDE" cables available, that "work like" an enclosure, but lack a physical case. Here is a picture of one: Picture. They are sometimes a little less expensive, and usually work well for very short term use. The drive is "out in the open" and unprotected while using these devices, so they are not intended for permanent usage.
Method THREE:
I call this the "Bootable CD method". ** THIS IS PROBABLY THE VERY BEST METHOD TO USE FOR LAPTOP DATA RECOVERY **
Costs: Likely free, if you have a windows xp cd with at least service pack one on it.
Difficulty: This is probably pretty hard to do if you don't have a broadband connection, as you will need to download large files. You will also need a CD burner, and mastering/burning software. You will need to already be familiar with, or learn how to turn ISO files into working CDs. If you are already able to do these things, this will be an easy project for you. If not, you're better off trying one of the other methods listed here.
Disclaimer: To use this method, your system should be physically sound - it must be able to at least P.O.S.T. and detect the hard drives/CD drives in the system. If it won't P.O.S.T., you probably have an underlying hardware problem, like a dead power supply, or a bad motherboard. You'll have to use method ONE or TWO to get your data back.
What to do: With this method, our intention is to build a bootable CD that will boot the dead system, and allow us direct access to our still-installed hard drive. There is NO need to open the case, set any jumpers, etc.
Go to either The BartPE website, or The Ultimate Boot CD for Windows (ubcd4win) Website, and read the instructions for building either of the bootable discs. It should take an "experienced" person an hour to make one of these bootable CDs. An "inexperienced" person may have a great deal of trouble making a working CD. Unfortunately, due to copyright restrictions, it is illegal to simply provide someone with pre-made, working CD. So you'll have to "build" one on your own. The ubcd4win CD also has several utilities for diagnosing and repairing hard disk errors, and for recovering deleted data, etc, but the use of these programs is beyond the scope of this guide. One should not use them unless they know what they are doing, because there is great risk of making the problem worse.
Once you get a CD built, you use it to start the dead system. You may have to "press any key", or tell the system to start from the CDROM drive. Eventually, these special CDs will start your system, and you can use one of the included file management tools to find and recover your data. You will need an external hard drive hooked to the computer (hooked up AND turned on before the system itself is booted) to COPY your data off to.
Once the CD is made, this is really the most popular way to recover data now. I can recover data from almost any non-bootable system in only a matter of minutes with these CDs. The hard part, unfortunately, is getting the CD made in the first place.
Method FOUR:
This is what I call the "Ghost Method", because you'll need to purchase Ghost 10/Ghost 2003 (2003 is included in the same retail box)
Costs: Sometimes Ghost is nearly free after rebates, sometimes it is $75+ if not on sale, or no rebates are available.
Disclaimer: Again, your system must be physically sound - able to P.O.S.T. for this method to work.
What to do: The Ghost 10 CD is bootable, just like the other special boot CDs mentioned above. If you can't make one of them, go buy one in the form of a Ghost 10 CD that will also boot your system. Once booted with the Ghost CD, there is a "recovery environment" where you can recover files and folders. Use this function to COPY your files to an external hard drive.
Alternately, the Ghost 2003 is also bootable. You can use it to image your "bad" hard drive, and then later you use the included Ghost Explorer program to "open" the image file, and extract your files back out of it. With Ghost 2003, you can actually image your system directly to your already installed CD Burner or DVD burner in your system, if you have one. This can save you from having to go and purchase an external hard drive to copy your data to.
I use this method all the time, and it works great. But Ghost 2003 is not an easy program for beginners, and be aware that Ghost is a very powerful program, and can actually destroy all of your data if used incorrectly. READ THE MANUAL before using it!
EDIT: Acronis True Image works in a very similar manner as Norton Ghost. If you can't find or afford Ghost, True Image is likely to work for you just as well, except that it is not able to write directly to CDs and DVDs.
There are also other methods available, including using Linux LiveCDs like Knoppix to boot systems for file recovery. You can find more information about Knoppix (and similar LiveCDs) in the Guide to Linux and alternate operating systems
There are even ways of networking your "bad" system to a good one, using these bootable CDs and LiveCDs, and copying all of your files over the local network (or Internet) for safe storage, but these techniques are pretty complicated and not for novices.
Finally, if none of these methods worked for you, it's likely that either the hard drive itself is "dead", or perhaps you've not followed the directions properly. Feel free to start a new thread and ask for help. We'll ask you to do a few troubleshooting measures, so we can see if your drive is even detected by your computer's BIOS still, stuff like that.
Hopefully this helps somebody! I'm open to hearing of other methods that people know of that are easy enough for the average person to use! This document will also be edited from time to time with clarifications as need.
Good luck!
Maddiebeagle
P.S. Interesting reading: Recovering Unrecoverable Data - a whitepaper
