Maybe, you are good enough to get your lost data all by yourself after reading this article.

Case 1: computer crashed, can't boot into system

This is considered the most common case, and also relative easy to get those data back.

First, you need to know why you can't boot into the system.

• Virus infected the system

• A system patch was not done successfully

• Some Windows level system file/dll corrupted

• etc ...

Normally for these situations, the first thing you may do is to reinstall the Windows System, and most likely, you may lose all your original files under system drive (C Drive for most cases).

However, the right to do is copy out all essential files from the corrupted system. Files like outlook emails and contacts, files you put under desktop, files under your default "My Documents" folder, bookmarks, etc, should be valuable data to the users of that computer.

There is a few ways to copy things out:

• Using a Bootable CD which has some build-in OS inside. That CD should be able to access all your original C Drive & D Drive. You can user an external drive to copy things out or you can copy valuable data into non-system drive, say D Drive. 
  
  The most famous CD is "Ultimate Boot CD", you can download it from here: http://www.ultimatebootcd.com/.
  
  Burn the ISO image into a bootable CD, then boot it. Inside you should see many operations available for you. You need to be a good technical guy to use this CD.
   

• There is another similar project created with Windows XP system. The CD operates like normal Windows XP system, and loaded with many tools inside. 
  
  The CD is called "Ultimate Boot CD for Windows" and you can download it from here: http://www.ubcd4win.com. 
  
  Some of the tools in the CD may not work properly, so use it with care. But basic functions to copy the files out should be working fine.

The above two ways assume that your CD rom is working properly and your system support booting from CD or DVD Rom. Booting from CD need some settings in the BIOS level: change the CD as the first booting device.

Read the two sites for the complete information about how to use them.

The worse situation, you can't boot from a CD for some reasons. 

For this case, you have open up the computer, take out the hard drive, connect to some external tools, such as IDE/SATA to USB. Then use a working PC or Laptop to copy all valuable data out. 

One very important thing is that, you must know where to copy those files. For example, for Outlook Express, the data for emails & contacts, by default, are stored in a very secret place ... You can locate that place by getting the directory path from a working PC's outlook. It is a long story so I will talk about that in another article in near future.

Case 2: Recover Deleted Files from Working PC or Non-working PC

This is a bit tricky case. Some people delete files by mistake, and clean the files from Recycle Bin. Well, still can be recovered, possibly.

The first thing to do is DO NOTHING. Don't use that computer. Just don't use it. This is to prevent those deleted data overwritten by your actions.

And go to back to Case 1, and try to boot the system with a bootable CD. 

Some tools inside the CD could assist to recover those deleted files, but no guarantee.

The tools are: "Handy Recovery", "File Recovery". Use the tools properly you may be able to get back some files.

You can find the complete instructions from here: http://www.pcinspector.de/Sites/file_recovery/bedienung.htm?language=1 

Case 3: Recover Data from Spoiled Hard Disks

This is the worst case. The hard disk is not accessible with normal Windows Systems, even BIOS is not able to recognize the drive.

When this thing happens, the first thing to do is to stop using it. Attempt to re-connect to the drive will only cause losing more data, as the high speed spinning drive may be further damaged, depends on the situation.

Normally to recover data from these drives, some kind of clean room is needed. Hard drive manufacturers or some special labs are able to do. They will use the special hardware to open the hard drive and process the data disks one by one to copy things out. 

Also, no guarantee all data will be recovered. Say, those data in bad sector area will be lost forever.

This article just put some simple summary for data recovery. The actual operations and situations are more complicated. Well, if your situation is the simple one, you should be able to get some hints how to get your data back.

The best thing to do, is to backup your data regularly.