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Riddle me this Batman: How can a HDD cause corrupt text in DOS & BIOS?

I haven't got the faintest clue how this could be possible. The only thing I can come up with is a boot sector virus, but even that sounds weak because I can't see how it could affect BIOS.

Bottom line this is an HP 17" Laptop with two hard drives in it and the client wasn't even using the 2nd HDD. The OS was corrupt. I salvaged all the data first off, but I could not repair the OS install and CHKDSK reported file errors it could not correct. Drive passed factory diagnostic and I also did a Spinrite level 4 on it just in case.

So I nuked the boot partition and used the factory recovery partition to do a factory restore. Seemed to go okay but when I booted into Vista the first time I got that dreaded Vista Windows Repair Wizard telling me Vista could not be booted and could not be repaired (same problem it was having before).

Now during all this time when I ran my DOS based diagnostics (Spinrite, WDC HDD Diag, MEMTEST86+, etc) I was getting corrupt text (numbers were okay but letters were randomly replaced with other random ASCII characters inconsistently). This made using the utils difficult but I could still make out what it was saying. This was only happening in DOS and BIOS so I just assumed it was a separate issue with the video chip since everything looked fine in Safe Mode and in WinPE. I have seen video cards in the past with a defect that would affect DOS but not Windows because the memory for DOS text is not addressed from Windows.

The laptop is not using shared memory for video but I ran MEMTEST86+ anyway in case the memory bus was compromised, and it passed.

Next step was to try a new drive so just I just pulled the spare out and put it in the main slot and took the old drive out, wanting to save her the cost of a new drive. The first thing I noticed was that the corrupt test issue was gone in BIOS now. I then ran Spinrite & MEMTEST86+ to confirm that the text looked fine in DOS as well. WTF?

Installed the factory recovery image from her emergency discs that she had actually taken the trouble to make when she bought the PC, and Vista booted up just fine.

The old drive still passes every test I've thrown at it. To play safe I have it on the Drive Erazer right now just to make sure that if there IS a boot sector virus that it's gone. I do not intend to put that drive back in there though. What I will do is throw a copy of an Acronis backup of her new OS installation on it that I've already made (just going to copy it from my external HDD to this drive using my bench PC) and tell her to hang onto the drive as an archive backup.

So I'm left with a mystery. HOW THE HELL could a hard drive corrupt DOS fonts? Especially in BIOS before the OS has even booted? I can't see how even a boot sector virus could do that.

If it was my laptop I'd put the old drive back in and mess with it some more, but this has already wasted a whole day and I have other customer PCs sitting on my bench waiting for attention. Sometimes you just have to walk away from these mysteries, but it does nag at me.

Anything I can think of doesn't explain it. A bad HDD controller could cause this if it was overwriting address space being used by the video card, but the controller is fine. I've installed Vista, SP1 & SP2, all updates and software on the other drive and it's running like a champ.

Any of you guys ever see something like this?

May be a motherboard issue where having the second drive attached causes power draw issues or something of the like. I've had similar experiences, but not the exact same. It's probably one of those so simple that it's stupid things or it may be one of those something's just plain broke (and not likely the hard drive). I will say that I've had a bad (or going bad) hard drive make even the BIOS go funky. I believe that when that happened that it wasn't the actual disk that was going, but the controller board on the drive. Sure can't explain how it affected the BIOS though.

that's my guess too...something bad on the mobo or possibly the drive mechanism is failing on an electrical level, putting out interference or noise of some sort. strange indeed.

Could be a bad control chip on the hard drive itself, or something more as a possible corruption with the hard drive's firmware. Short to say, I think we all have run into our own little computer mysteries. You might be able to put the drive back in and everything works just fine for no reason. Sometimes things don't work or work for no noticeable reason.

Mobo is fine, that's why this is driving me nuts. The laptop is back in the client's hands. Rock solid. It's definitely the drive because it's consistent: put the old drive in and the fonts in DOS & BIOS are corrupt. Pull it out and put the good drive in and they're fine. Tried it several times.

I wiped the old drive with my Drive Erazer and put an Acronis image file of the new install on there, wrapped it in bubble pack and gave it to the client as an archive backup.

makes me wonder if the HDD wasn't sending some wrong codes (background app) to the CPU causing an ASCII text error... Couldn't tell you if it was boot sector or not though, all my boot sector virii killed my HDD's, and never ran into a malicious code that would switch characters in ASCII.

Consider this riddle to still retain it's mystery (I'll go see if i can find something on it though).