System Boot Process
In most cases, the first indication of a problem with hard drive data is a
refusal of the machine to boot properly. For the computer to be
able to find startup partition and to start booting, the following conditions must apply:
- - Master Boot Record (MBR) or GIUD Partition Table (GPT) exists and is safe
- - Partition Table exists and contains at least one Active partition
- - Active partition contains all necessary and not damaged system files for the OS launch
If the above is in place, executable code in the MBR selects an active
partition and passes control there, so it can start loading the standard files (COMMAND.COM,
NTLDR, BOOTMGR, ... ) depending on the OS and the file system type on that partition.
If these files are missing or corrupted it will be impossible for the OS to boot
- you understand the situation if you have ever seen the famous "NTLDR is missing ..." error message.
Volume Visibility
A more serious situation exists if your computer will start and cannot see a
drive partition*. For the partition to be
visible to the Operating System the following conditions must apply:
- - Partition/Drive can be found via Partition Table
- - Partition/Drive/Volume boot sector is safe
- - Volume system areas (MFT, Root) are safe and accessible
If the above conditions are
true, the Operating System can read the partition or physical drive parameters and display the
drive in the list of the available drives.
If the file system is damaged (Root areas on FAT12/FAT16/FAT32/exFAT, or Master File Table (MFT) records on NTFS) the drive's
content might not be displayed and we might see errors like "MFT is corrupted",
or "Drive is invalid" ... If this is the case it is less likely that you will be
able to restore your data in full. Do not despair, as there may be some tricks or tips
to display some of the residual entries that are still safe, allowing you to
recover your data to another location.
Partition Recovery Includes
- - Physical partition recovery. The goal is to identify the problem and write
information to the proper place on the hard drive (to MBR and Boot Sectors) so that the partition becomes
visible to the Operating System again. This can be done using manual Disk Editors along with
proper guidelines or using partition recovery software, designed specifically for this
purpose.
- - Virtual partition recovery. The goal is to
determine the critical parameters of the deleted/damaged/overwritten partition and render
it open to scanning in order to display its
content to copy important data to the safe place. This approach can be applied in some cases when physical partition recovery
is not possible (for example, partition boot sector is dead and physically unreadable) and is commonly used by
file recovery software. This process is almost impossible to implement it manually.
Other Hard Drive Partition Recovery Topics
These topics related to the recovery of partitions apply to any file system:
For these topics the following disk layout will be used in the examples:
The figure shows a system with two primary partitions - C: (NTFS) and H:(FAT) and one extended partition having two
logical drives - D: (FAT) and E: (NTFS)
*Note
that if your computer has two operating systems and you choose to start in
Windows 95/98/ME or Linux, these operating systems cannot see partitions that are
formatted for NTFS. This is normal operation for these operating systems. To
view NTFS partitions, you must be in a Windows NT/2000/XP/2003/Vista/7 environment.
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