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Fdisk /mbr and Slaving drive with Win 98

Posted on 2003-11-03
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Last Modified: 2013-12-28
Hello,

I'm troubleshooting a computer for a friend.  The computer is running Windows 98 and won't boot past the Windows startup page.  The computer can't be booted via safe mode either.  I strongly suspect it's a MBR problem, as scandisk within the Windows set-up exported that there was a data error in FAT sector zero.

I'm planning on booting from a Windows boot disk and using fdisk /mbr.

However, I have some concerns, as I'm not 100% certain there are no drive overlays.  The data on this computer is extremely important for my friend, as they have their only copy of their master's thesis on there, along with many family photos (Yes, pretty insane to not have a backup, but a little late for them now).  What should I watch out for with MBR to ensure that none of the data, or the partitions are destroyed?

I'm thinking of making the drive a slave on another Win 98 machine, so I can transfer the files prior to attempting the fix.  I've never done this before with a drive that is non-bootable and has an operating system already installed on it.  Any issues or special steps which I should be aware of before hooking up the drive (aside from ensuring the jumpers are correct)?

Thanks.

Auriclus
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Question by:Auriclus
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by:war1
ID: 9673973
Auriclus,
    I would advise putting the drive as a slave on another computer and reading the data from that. There is no issue if you just want to read data.

fdisk /mbr is an agressive way of cleaning a drive.  It can cause problem, so I would advise this method as a last resort.
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by:Auriclus
ID: 9674554
That's fine.  I'd like to hear from anyone else who has comments on this or knows of a better way to restore a corrupt MBR.

By the way, this problem occured from the user downloading a windows update from Microsoft (they didn't specify which) and then once they rebooted the computer, they realized it wouldn't boot any more.
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by:LeeTutor
ID: 9674765
Here's an MSKB article that may be of help in determining if your computer uses a drive overlay:

http://support.microsoft.com/default.aspx?scid=kb;en-us;186057
How to Tell If Drive Overlay Program Is Installed in Windows

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by:LeeTutor
ID: 9674779
I also do not trust the often given advice of using fdisk /mbr.  Here's a page I found with some good arguments against it:

http://www.cknow.com/vtutor/vtfdiskmbr.htm
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by:Auriclus
ID: 9674892
Thanks for your comments, LeeTutor.  The both links are interesting, especially the knowledge base article.

However, the question remains, if I do not use fdisk /mbr to fix the corrupted boot record, then how else am I going about it?  I plan to back-up the data first by slaving the drive, so there should be no major consequences if it fails, save a reformat and reinstallation of Windows.
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by:LeeTutor
ID: 9674902
Well, if you plan to backup the data by slaving the drive, then there is no reason not to try fdisk /mbr afterwards, for despite the reservations published in the article I gave the link for, it does sometimes work.
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by:spiderfix
ID: 9675587
If your is truly interested in recovering their "master's thesis" and
"family photos" then you should not experiment with their computer.

Nobody has even mentioned trying to read the drive by booting
from a boot disk. If your friend's data is important then you'd
best not touch the machine, especially if you haven't a technical
background.

You want to get that computer in the hands of someone qualified
to recover the hard drive. You don't want to be running fdisk /mbr
and finding out that kills the drive totally.
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by:Huseyin1
ID: 9677540
Hi

I think all you need to do is a scan disk, this will fix the MBR, do scan disk in DOS mode, also when you boot using the 98 boot floppy disk type WIN to see if wiondows can install, then do the scan disk that way first.

H
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by:Auriclus
ID: 9683129
I ran scandisk in DOS mode and it reported the same error I got previously when scandisk ran off the Windows installation CD:

"Scandisk encountered a data error while reading the FAT entry for cluster 0.  This error prevents scandisk from fixing this drive."

I removed the drive a slaved it in a Windows XP machine.  XP recognized the drive, however, if I tried to access it, it reported "The parameter is incorrect".  The drive shows up as zero bytes, in RAW format.  I loaded Norton Utilities onto the box, but it didn't help, as the drive is not useable.

The data, however, is accessible via DOS mode, although it runs quite slowly.  Is there a possiblity I could slave another drive into the problem computer, back-up the files in DOS by tranfering to the slave, and then finally attempting the FDISK /mbr?

Comments?
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by:Auriclus
ID: 9697793
Well, I've slaved another drive and successfully copied the person's data via DOS.  All the file names are of course now trunucated because of DOS but that's of litlle consequence. That was the most important step, now I can do whatever I feel necessary to get the computer in working order again.

Now I'm looking for a good dos-based drive utility which can repair the FAT table.  I tried the demo version of Hard Drive Mechanic, but the the program would not start from the disk and just displayed a blinking cursor.

Anyone have any recommendations for good tools?  I'd prefer a list of tools that you've actually worked with before and were able to resolve problems with rather than a blanket list of every hard drive utlity on the market.

The winner, of course, gets points, as no one here is yet ahead in helping me resolve my problem.

Thanks.
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by:Auriclus
ID: 9697826
Oh, by the way, the fdisk /mbr did not work.  It didn't make things worse or better, it's the same as before.
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rogue_phoenix earned 170 total points
ID: 9698048

FAT and MBR are two different thigs. MBR sets up partitions and tells the BIOS which one is bootable (active); if that wasn't working you'd see something like "operating system not found" right after POST. FAT - File Allocation Table -- tells the operating system (DOS, windows, etc.) where to find the files on the partition.

If you've got the important data off (and verified it), I'd reccommend reformatting it.
If there are bad sectors in the FAT (a likely cause of your problem), the best a repair utility is going to do is mark them bad and salvage what it can of the FAT. Which means you're going to have an indeterminate amount of hard disk data  suddenly 'vanish' (sounds like some of the 'known' vanishing files are in the windows directory). Even undelete utilities use FAT entries; when you use the del command, it overwrites the first character of the filename in the FAT, and undelete utilites look for this.


simple FAT
-------------
file1.txt    cyl 7 head 3 sector 3354
#ile2.txt   cyl 49 head 2 sector 4431   <-- recently deleted file
file3.exe   cyl 35 head 0 sector 8923    etc.

If you have a bad secor in the FAT, whole sections of this table are irrecoverably lost, therefore useless to an undelete utility. At this point you'd need a utility that scans the surface of the disk, sector by sector, and finds data that is neither referenced in the FAT nor referenced by any other sector on the disk. I've never done that so I can't help you locate tools for it. If you can find one, I'd like to know about it, but in my experience once you get that deep into it you're going to a data recovery specialist. On a really big disk, this is a mathematical operation on the scale of cracking SSL encryption (or worse). Your time is really better spent formatting & reinstalling.

Even with a utility that could fix the FAT, I'd still use the drive just long enough to get my data off (which you've already done), then format it anyway.  Format is the ultimate disk repair utility ;)



afterthought: FAT sector 0

this article is about win2k, but it has some interesting information about FAT32, including mentioning a backup of FAT sector 0.
http://support.microsoft.com/?kbid=246146

Here's a better article:
http://www.dewassoc.com/kbase/hard_drives/boot_sector.htm

this looks like a promising editor:
http://www.omnixray.com/

You're into some really specialized knowledge here. If it were mine, I'd still FFR.
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by:war1
ID: 9712153
Glad you got your data saved.  Is there a reason you cannot run boot up with a startup disk now and run Fdisk and Format on the bad drive?
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by:Auriclus
ID: 9732685
Thanks for your detailed and extended answer, Rogue_Phoenix.

I will be performing a reformat and reinstall after all as nothing else seems to be working.  The data is safe and that is the imporant thing.

Interesting, I've been able to trace the root of the problem.  The person who was using the computer last told me they downloaded an Intel video driver from Windows Update (they have onboard video) and upon the second boot after installing the drivers, the PC locked-up.  I looked up their motherboard model and went to the Intel website, and sure enough, within the release notes for the most recent bios flash update, it clearly states: "Corrected video corruption and system hang when the setup question "Fixed Disk Boot Sector" is set to "Write Protect" and an OS attempts to write the boot sector."

Thus the problem: crappy bios design.

Thanks all for you help.

Auriclus
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by:Auriclus
ID: 9767859
I've dug a little deeper and I've come up with an interesting observation.

If virus protection for the boot sector is turned on for FAT32 drives, then the drive will fail to boot.  It seems that with this particular bios and motherboard, under the right conditions it can be be fatal.  Otherwise it would just say that a disk error had occured writing to drive C:. Going back into the bios and checking off virus-protect would of likely solved the problem if it had been recoverable.
 
http://www.firmware.com/support/bios/fat32wp.htm

Auriclus
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