Partition Recovery Process
System Boot Process
In some cases, the first indication of a problem with hard drive data is a refusal of the machine to perform a bootstrap startup. For the machine to be able to start properly, the following conditions must apply:
- Master Boot Record (MBR) exists and is safe
- Partition Table exists and contains at least one active partition
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, ... ) depending on the file system type on that partition.
If these files are missing or corrupted it will be impossible for the OS to boot - if you have ever seen the famous "NTLDR is missing ..." error, you understand the situation.
When using Active@ UNDELETE, the recovery software accesses the damaged drive at a low level, bypassing the standard system boot process (this is the same as if you instructed the computer to boot from another hard drive). Once the computer is running in this recovery environment, it will help you to see all other files and directories on the drive and allow you to copy data to a safe place on another drive.
A more serious situation exists if your computer will start and cannot see a drive partition or physical drive (see Note below). For the partition or physical drive to be visible to the Operating System the following conditions must apply:
- Partition/Drive can be found via Partition Table
- Partition/Drive boot sector is safe
If the above conditions are true, the OS 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, FAT area on FAT12/FAT16/FAT32, or system 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. 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 describes two things:
- Physical partition recovery. The goal is to identify the problem and write information to the proper place on the hard drive so that the partition becomes visible to the OS again. This can be done using manual Disk Editors along with proper guidelines or using recovery software, designed specifically for this purpose. Active@ Partition Recovery software implements this approach.
- 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. This approach can be applied in some cases when physical partition recovery is not possible (for example, partition boot sector is dead) and is commonly used by recovery software. This process is almost impossible to implement it manually. Active@ UNDELETE, Active@ UNERASER software both implement this approach.
Other Partition Recovery Topics
These topics related to the recovery of partitions apply to any file system:
- Damaged MBR
- Partition is deleted or Partition Table is damaged
- Partition Boot Sector is damaged
- Missing or Corrupted System Files
For these topics the following disk layout will be used:
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))