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From: wtm@neoucom.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: Probable non-DOS disk message
Message-ID: <582@neoucom.UUCP>
Date: Tue, 12-May-87 10:10:32 EDT
Article-I.D.: neoucom.582
Posted: Tue May 12 10:10:32 1987
Date-Received: Thu, 14-May-87 05:54:48 EDT
References: <226@eli.UUCP>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 46
Keywords: DOS non-disk error_msg
Summary: Try rebooting your system and run CHKDSK again

In article <226@eli.UUCP>, geller@eli.UUCP (David Geller) writes:
> Here's the message I get when I run chkdsk on an AT
> compatible with a WDC controller and a Seagate 225
> 20Mbyte HD:
> 
> 	Probable non-DOS disk.
> 	Continue (Y/N)?
> 
> Typing either Y or N doesn't seem to do anything. The
> chkdsk completes and everything on the system seems
> quite normal. Any clues?


I've seen this happen when you have a BUFFERS=nn line in your
CONFIG.SYS file.  Sometimes, an errant application program will
trash the copy of the FAT that is in the RAM buffer, thus causing
the message, eventhough there is nothing wrong with your disk.

Usually, rebooting the system is enough to make the message go
away.  If you still get a nasty message after rebooting, try
booting up from a floppy with no CONFIG.SYS file.  See if you still
get the message.

If all else fails, the boot block of your disk could contain an
error or errors.  The drive's partition table begins at offset 1BE
(DOS 3.1) in the boot record (physical sector 0).  The byte at 1BE
is the boot indicator for partition 0.  Byte 1CE is the boot
indicator for patition 1.  1DE for partition 2. 1EE for partition
3.  A drive can have only one bootable partition.  For the bootable
partition, the byte should be 80H.  For all other partitions, the
byte should be 00.  1C2,1D2,1E2,... are the operating system ID
bytes for the respective partitions.  For this, 00=unknown type,
01=DOS, 12 bit FAT, 04=DOS, 16 bit FAT.  See  page 9-6 to 9-8 of
the IBM DOS 3.1 technical reference manual for further details.

You might consider taking a peek at the boot record with DEBUG or
the Norton Utilities if the message persists.

Hope this is of some use...
  --Bill

Bill Mayhew
Division of Basic Medical Sciences
Northeastern Ohio Universities' College of Medicine
Rootstown, OH  44272  USA    phone:  216-325-2511
(wtm@neoucom.UUCP   ...!cbatt!neoucom!wtm)