Hard drive total loss of data

thirolle used Ask the Experts™
This has happened twice, with two different hard drives, each of which was attached as the only drive (master) on IDE 2:
In the middle of writing some files to the drive, the file structure on the drive suddenly gets totally screwed up. If I look at the drive contents in Explorer, I see garbage characters instead of the folder names that should be there. When I reboot, the drive can no longer be accessed. I think what has happened is that the boot sector, or FAT tables, or both, have been overwritten. The partition table info seems to be OK, though (as viewed in fdisk).

If I use a utility to view data in drive clusters, it seems like there is no valid boot sector, and I cannot find the FAT tables. The file data is still there, for the most part, though it is hard to retrieve without the FAT table info.

With the second drive, it seemed like this drive problem happened just as I was passing 32 GB of data on the disk, which made me begin to wonder if there was a bug in the BIOS related to the 32 GB limit - tho' the BIOS does report the hard drive size correctly.

The first drive was a 40gig, second was a brand new 80gig. My mobo is an Asus with KT133 chipset. I am using an old Dell 250W power supply.

BTW, I reformatted the second drive and have been using for a couple of weeks now with no problems - have gotten up to about 20gig of data on the drive now.

Can someone please suggest what might be wrong here? Can the power supply cause this kind of a problem? Or bad cables or mobo or what?
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Auerelio VasquezETL Developer

Try using fdisk/mbr
did you use the same IDE cable both times??
and what make is ur HD?? some are known to be nothing but problem i.e. 75GXP's famous click of death, check the web to see if this is a common problem for ur HD model.

could well be a virus, try http://housecall.trendmicro.com/ for a free online virus check.  if you dont want to register then click this link, http://housecall.trendmicro.com/housecall/start_corp.asp it takes a while to load.
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ohh, good point twotwenty, ultra dma cables in particular, are suseptible to damage through moving pullin and folding.  but the old ones arent that great either, try another one.


Yes, I did do a virus check, two actually, with ScanPM and FProt, booting from a clean floppy in both cases, and they found nothing, so I don't think this is a boot sector virus.

Yes, it was the same IDE cable in both cases. It is the same IDE cable I am using now, with no apparent problems currently.

First HD was a Maxtor 40gig, second a brand new Western Digital 80gig (not my fave, but got a good rebate).

Could a weak or old power supply cause such weird symptoms?

Thanks all for your responses.
What OS are you using?
unlikely to be the PSU, it could still be the cable though, I had the same problem a year ago where I couldnt access data and it all lookup screwed up.  I formatted the drive a number of times before I twigged and changed the cable.  I found the problems were intermittent and i could get through most of an install or i could get through a whole one but soon after it would die.  give it a try it is well worth it.

also try it on the secondary ide channel.


I am using Win98SE.

Changing the IDE cable is easy enough, so I will try that. Thanks for that suggestion.

It seems like all kinds of weird issues can be related to a bad PSU, so I began to wonder if this could be the culprit. My PSU is about 6 years old, I think. If it supplied power unevenly, could this cause the drive to write to the wrong part of the disk, thereby overwriting the critical sectors at the beginning of the disk?

This is one of those difficult & annoying problems because it is intermittent. I can go for days or weeks with no problem, then BANG! No data...  This means that it will be a long time before I know that this problem is licked. Meanwhile, I hold my breath and hope my drive does not blow up again :-)

Thanks again for your help.


I replaced the power supply and IDE cables, only to have my hard drive crash again when it hit ~30-32GB of data. So my best theory now is: there is something wrong with the BIOS or IDE controller on this mobo, such that when the hard drive tries to write to a portion of the drive beyond the 32GB limit, it actually begins writing over the beginning of the drive - i.e., the MBR, boot sectors, FAT tables, etc. - thereby effectively rendering the drive useless. No physical harm is done - each time, I have been able to reformat and reuse the drive with no problem.

I am not sure if this is a problem with the Asus A7V-VM (an OEM board made for HP, which they call "Tahiti") in general, or just mine.

I bought a Promise PCI IDE controller, put my big drives on this, and problem is gone :-) I was able to put 50GB of data on my 80GB drive, no prob.

Ah, well, I knew this was a weird one... Thanks to everyone for their ideas.
For the edification of anyone else coming across this thread: the symptoms I experienced were, I think, the "normal" results of trying to use a hard drive larger than the BIOS could handle. Even tho the BIOS could apparently "see" the full size of my HD (i.e., it looked properly configured in BIOS setup), it could not read/write over the 32GB limit. So.. the lesson is beware using drives over 32GB on mobos of KT133 vintage or older.

I found the best writeup of hard drive limitations and barriers at:


According to this site, what I experienced is called "wrap-around": I quote:

"Many an old BIOS will presume that the number of cylinders in a drive will always be 1,024 or below, and therefore will only look to the bottom 10 bits of the cylinder number reported by the hard disk (2^10 = 1,024). As a result, when drives report cylinders over 1,023, the BIOS counts up to 1,024 and then wraps around to zero and starts over."

This results in drive overwriting the first few sectors of the drive, which is where all the MBR, partition info, and FAT table info is, therefore causing your partition to go bye-bye. No damage to the drive, but any recovery of data is nearly impossible.


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