Recovering data from hard disk with corrupted partition table

at 11:03 PM Labels:

Last weekend I accidently overwritten the partition table of my dell inspiron mini 10 while trying to install the grub4dos mbr.
I was trying to dual boot windows 7(default OS which came with the Netbook) and windows xp operating systems. Since Windows XP was installed after Windows 7, my netbook was not able to log in to windows 7. I did some experiments like using easyBCD, windows 7 recovery from USB drive etc to boot windows 7. But it did not work.
After doing some research with the help of different tools, I found that problem is due to having different primary partitions. While booting, bios will check for a partition with boot flag set and loads the boot code from that partition. When windows XP is installed, it updated the boot flag such that partition with windows XP is bootable. So the recovery tools were updating the windows 7 boot partition, but the boot flag was set for the XP partition. So only Windows XP was booting.
While I was trying different tools, I have erased the boot partition of Windows 7. So I decided to install grub4dos with its files on the boot partition.
My plan was to create a bootable USB disk using and then install grub4dos from the commandline interface of grub boot menu displayed by the.
But unknowingly I typed 
dd if=(fd0)/grldr.mbr of=(hd0)     => Wrong method

Instead of doing the steps 
dd if=(fd0)/grldr.mbr of=(sd0) bs=440 count=1
dd if=(fd0)/grldr.mbr of=(sd0) skip=1 seek=1
which will leave the partition inforamtion and write only the mbr. 
Partition Layout - Before writing mbr wrongly
Partition Layout - After writing mbr wrongly




Because of the wrong command, partition table is overwritten by grldr.mbr. When I rebooted, grub4dos was giving error that it cannot find the grldr because of the corroupted partition table. While trying commands root (hd0,0) grub reported that the partitions cannot be found. When I checked with the gparted live boot CD, it reported hard disk to be empty.
Eventhough the partition table is erased, data contained in the disk is available. Fortunately I had a multiboot CD containing Bart PE. With getdataback NTFS software, I was able to recover the data from hard disk.
Steps involved are
  1. Booting the Bart PE CD from external CD drive(Can be done from a USB flash drive also). While booting, also connect an external disk drive big enough to hold the recovered data.
  2. Scanning the hard disk using the getdataback NTFS(or FAT depending on the partition types).
  3. Getdataback software will list the possible partitions after the scanning.
  4. Save the scan data at this stage so that it can be loaded again for restoring another partition. This will help saving the time need for scanning the disk agiain.
  5. Select the correct partition from the list. Correct one can be identified by checking of size of the partition.
  6. Copy data to the external disk drive.
  7. Repeat the steps for another parititions. 
Screenshots of using getdataback





2 comments :

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