View Full Version : what has happened to my hard disk?

November 29th, 2017, 05:27 PM
Hi everyone,

Today I tried hooking up my 40MB Seagate ST-157a from my AST 286 up to my modern Win10 PC to copy over some files. To my surprise this worked just fine, windows recognized the disk and was able to read and write to it. I reattached the drive to my 286 and everything was working well and I was able to play some new games I had copied over. I realized there were some files I forgot so I reconnected the drive to windows and copied the rest, this is when things went awry. When the disk was reconnected to my 286 it would not boot. I got the standard "NON SYSTEM DISK OR ERROR". The disk will read in windows and in dos when booting from the floppy but it simply will not boot.

At this point I have tried reformatting the disk, reinstalling DOS onto it but still nothing. Anyone know whats going on with the disk? is it dead? I don't care about the data on the disk its all just copies of stuff I have elsewhere however I would very much like to continue using it. Is there anything I can do to get it working again?

November 29th, 2017, 05:42 PM
I had a similar "this doesn't make any sense" issue with an ST157A last week.
Had a MS DOS 6.2 install on it, would not boot. Did DOS installs using the original installer (DOS 5), and doing SYS commands (DOS 5 and DOS 6), and it wouldn't stick - always "non-system disk or disk error".

So I did FDISK /MBR, then did SYS A: C: - and that cleared it up. Now it boots like a champion.

November 29th, 2017, 06:09 PM
Just gave that a shot, Unfortunately no luck.

You just ran fdisk /MBR from the a drive with no other parameters?


November 29th, 2017, 06:21 PM
Windows can do a lot of strange things to the partition table without telling you. Consider the Win95 "volume tracking" software clobbering floppy disk boot sectors silently.

What does FDISK show for partition information?

November 29th, 2017, 06:38 PM

that's what we get from fdisk

November 29th, 2017, 07:08 PM
You said it works fine after booting from a floppy. Is that so bad? You only have to boot it once and then everything's the same for the whole remainder of the session which can be hours or even days.

November 29th, 2017, 08:14 PM
Let's try something. Do you have a boot floppy with the same version of DOS on it?

If you boot that, what happens if you do a SYS C: from the command prompt (make sure that you have the SYS.COM on your disk)?

The should rewrite the partition boot sector and transfer new copies of the system files without erasing any other data on the drive.

November 29th, 2017, 08:17 PM
Already tried that, no luck. Maybe low level format?

November 29th, 2017, 08:22 PM
That seems to be a bit extreme, considering that you're not showing any surface errors (unless I missed something).

What does an CHKDSK C:*.* say when run from floppy?

Failing that, we can have a peek at your MBR using DEBUG. A LLF might cure the problem, but you're going to have to reload the whole disk if you do. I've seen this happen when the host machine thinks the geometry is different from the system that created the disk, but this is the system that originally made the disk, right?

November 29th, 2017, 08:59 PM
Actually this disk was made in a 386 I have. Forgot to mention that, I upgraded the drive in the 386 and moved this to my 286 cause I thought it would be more appropriate, I didn't think this would cause a problem.

November 30th, 2017, 09:49 AM
After changing some bios settings in my modern PC, I was able to get the drive to boot there but not in my 286. I wrote an image to the disk of DOS 5 which boots in my modern PC but again not in my 286 where I get "missing operating system", which is a different error message than before which was "NON SYSTEM DISK OR ERROR".

November 30th, 2017, 10:15 AM
I suspect that the machines view the disk differently vis--vis geometry.

November 30th, 2017, 12:52 PM
Chuck is right.

What are you using for C-H-S in the 286?

Remember, the modern PC can translate; the 286 can't.

November 30th, 2017, 02:11 PM
Even translations on PCs that can translate can vary. I remember having an HP Vectra (P1, maybe) that would only go as high as 254 heads, so the number of cylinders, etc. differed from a non-HP machine that used 255 heads. Others, IIRC, put an upper limit of 240 on the number of heads.

We sometimes forget the world before LBA, although SCSI has always done things that way.