TestDisk:Data Recovery Software
TestDisk is a powerful data recovery software, and was primarily designed to help recover lost partitions and/or make non-booting disks bootable. These may be caused by faulty software, viruses, or human error. With TestDisk, even partition table (a filesystem table that contains information about how many and which types of partitions are on the disk) recovery becomes really easy.
When a hard disk drive crashes, the first thing to do is to make sure no more data is written to the drive. If we have a situation where the partition table is all right, but critical operating system files have been damaged, Windows will not boot. In such a case, if there is another OS installed on the system under consideration, the HDD may still be read. So, you can gain access to the files on your hard drive with a crashed OS by booting the computer with a DOS boot disk and then use a DOS-compatible file recovery program such as TestDisk.
In addition, we should mention that transferring the HDD to another computer prevents the drive from being written to accidentally, and could allow you to retrieve information from the disk. At times, all that is required is to use Windows Explorer (on the system to which the drive has been transferred) to look through the file structures.

TestDisk is capable of restoring lost information in a matter of minutes. It supports all major operating systems, and also RAIDconfigured drives. It has Linux versions as well.
TestDisk queries the BIOS or the OS in order to find the hard disks and their characteristics. It does a quick check of the disk’s structure and compares it with the Partition Table for entry errors.
If the Partition Table does have entry errors, TestDisk can repair them. If there are missing partitions or a completely empty Partition Table, TestDisk can search for partitions and create a new table or even a new Master Boot Record (MBR) if necessary. Now, a master boot record (MBR) is the first sector (“sector zero”) of a partitioned hard disk, and is responsible for retaining vital system information such as the partition table, and the Bootstrap loader.
TestDisk has features for both novices and experts. For amateurs, TestDisk can be used to collect detailed information about a non booting drive, which can then be sent to data recovery professionals for analysis. Those more familiar with such procedures should find TestDisk a handy tool in performing on-site recovery.
1. Upon starting TestDisk, you get a screen at the top that lists your available physical drives.
2. Highlight the drive you wish to recover and select the Analyze option.
3. This will show the current partition structure, and upon hitting [Enter], will start searching the drive to see whether the actual partitions match. Make a point to take this information down.
4. Once this search is complete, hit [Enter] again. It’s a good idea to run the “Search!” option to do a more comprehensive search of the drives.
5. If you initially had no partitions shown because of a damaged or wiped partition table, TestDisk will now hopefully have rediscovered the partitions.
6. Verify the information and select Write to save the new information onto the disk. If removing your partitions was the only damage you did, you should now be up and running again.
7. If you have erased or damaged your Partition Table, nothing will be displayed under the listings, as above. In this case, you should select the “Advanced” option. The tool will assist you in revamping your HDD in the same manner, as above.
TestDisk will compare the boot sector to the backup boot sector. If they are identical, it can do nothing more, but if they are different, it will ask you if you wish to overwrite the boot sector with the information from the backup.
Link:www.cgsecurity.org/testdisk.html




