How to backup and Restore Data from a Corrupt Hard Drive

Dennis Faas's picture

Earlier this week I sent out a very controversial article to a few other online ezines (electronic magazines) in hopes of syndicating the Infopackets Gazette to help increase our readership.

If you haven't visited recently, you might have missed the intriguing article about Mcafee Anti Virus. The article questioned whether or not McAfee purposely mislead users to purchase an update to their Virus Scan software ($39.95), when in fact, it was not required for some users.

The article was an instant hit. It was published on a few major web sites and generated quite a bit of traffic to our site. The article was very well documented and the supposition was well supported: McAfee was caught red-handed misinforming their users. You may want to read the McAfee article now, and come back later to this article.

The beginning of the McAfee article started out with a prelude into the scandal. The whole reason for going to the Mcafee web site was to update my virus scanner definitions (DAT) because I wanted to rule out that a virus could have been responsible for corrupting my hard drive. After all, a virus scanner is only as good as its definition updates.

Oddly enough, I received quite a few questions from those who read the article asking, "how did you recover your data after your hard drive went corrupt?" Because of the technicality involved in answering such a question, I purposely did not go into great detail in my McAfee article. However, there are definitely some people who are itching to know! In light of this, I've decided to include the answer (in detail) in this issue of the Infopackets Gazette.

How to backup and Restore Data from a Corrupt Hard Drive

When attempting to backup data on a corrupt drive, the first thing on the list of items is to try and repair the drive using Scan Disk (Windows 95, 98, ME) or CHKDSK (Windows 2000 / NT / XP users). Since I ran Windows 2000, CHKDSK executes automatically every time Windows is booted if errors are detected on the drive.

In my circumstance, something was causing Windows to loop and reboot itself after completing CHKDSK. Since I was unable to "shut down" properly, the hard drive would corrupt itself again, and the whole operation would repeat indefinitely. I was now faced with the problem of not being able to get back into my system in hopes of retrieving / or being able to backup my critical files.

At this point, I decided that I needed to reinstall Windows and copy my information over to another (healthy) hard drive. In order to install a new copy of Windows, I would have to format the bad hard drive since Windows Setup does not allow Windows to install on a corrupt drive. Obviously, I did not want to do format my corrupt drive in order to install Windows, since I still needed to backup the information from the corrupt hard drive.

I opted to install Windows on a spare 6 gigabyte hard drive I had lying around. I formatted the 6 gig drive and installed Windows 98. Now I was able to run Scandisk and correct the FAT table (File Allocation Table) on the bad drive. The FAT table is simply a database which points to the physical location of each file on the hard drive. If the FAT table is incorrect, then it is possible to write over existing data on the bad drive.

That brings me to my next point: never ever attempt to write to a hard drive that is corrupt. That also means attempting to run (and correct infected files) with a virus scan on a corrupt drive could also cause further corruption of data. Always back up data first before attempting to virus scan a corrupt drive!

Scandisk and Check for Viruses

After ensuring the FAT table integrity of the bad drive, I checked for viruses with the latest DAT (virus definition) file. When the virus scan was complete, I copied my most critical files to the 6 gigabyte hard drive.

What is considered a Critical file?

A critical file is an original file that cannot be replaced from another source; an example of a critical file might be a document written by you. While I lost over 35 gigabytes of information, the majority of these files were not critical and could be replaced at a later date.

It is possible that some files may not copy.

Depending on how badly corrupt your hard drive has become (especially if the corruption has come from a hardware failure, such as a bad sector on the drive), you may not be able to copy over all of your critical files. I've witnessed strange things before which can cause a system to hang during a copy process because of a hardware failure -- such as a hard drive gone bad. If this ever happens, you may have to manually copy and paste each file to the destination drive -- one by one -- until you find the area of the hard drive that causes the system to hang. Obviously, the data on this area of the drive is beyond repair and may never be retrievable.

Reinstall Windows after the corrupt drive has been repaired.

After the backup was completed, I booted from clean floppy (virus free / write protected disk) and used a DOS utility called FDISK to format my 120 gig hard drive. FDISK automatically checks the drive for surface errors as it readies the drive for a format. If my drive was indeed experiencing a hardware failure such as a bad sector, FDISK would most likely run into it. If the FDISK operation was unable to complete, I would further suspect a hardware failure -- which could also include other items inside my machine, such as the hard drive controller on the main board, the hard drive cable, and anything else related to a hard drive I/O (input, output/read, write) operation.

Since I was able to complete FDISK, I restarted my machine, booted from the clean floppy once more, and then formatted my 120 gig hard drive. I proceeded to install Windows 2000; I then copied over my critical files back to the 120 gig hard drive. I opted to keep the 6 gig drive full of my critical files for a few more days until I was sure everything was in order.

To Recap:

  1. Install Windows on another hard drive
  2. Run Scandisk / CHKDSK on bad drive
  3. Virus scan bad drive
  4. Backup critical files over to temp drive
  5. Boot from clean floppy, FDISK bad drive, reboot
  6. Boot from clean floppy, format bad drive
  7. Reinstall Windows on corrected drive
  8. Restore backup files to corrected drive
  9. Keep temporary backup drive incase bad drive has hardware failure
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