Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!portal!cup.portal.com!Wes
From: Wes@cup.portal.com (Wes H Cowley)
Newsgroups: comp.sys.ibm.pc
Subject: Re: "Probable non-DOS disk" ??
Message-ID: <20902@cup.portal.com>
Date: 31 Jul 89 23:32:00 GMT
References: <24048@iuvax.cs.indiana.edu>
Organization: The Portal System (TM)
Lines: 24

> ... when I run CHKDSK I get the "Probable non-DOS disk" ...
> ... Can anybody tell me what triggers this message?  Especially, what
> triggers it and then comes up with a clean report?
 
Thanks to the people on Bix who helped me out when I had the exact same 
problem, I can give you the answer.  CHKDSK relys on the first byte of the 
FAT in generating or not generating that message.  Something has overwritten 
that first byte.  In my case I traced it to a compiler that just had to get 
the last word in when my disk filled up.   Unfortunately that it put that
word in the FAT.
 
For a hard disk, the first byte should be hex F8.  Get into your favorite 
sector editor, pull up the first FAT sector, and change that byte.  The next 
two or three bytes (depending on whether you have a 12 or 16 bit FAT, with a 
30M drive you'll probably have a 16 bit FAT) should be hex FF.
 
> Thanx for any advice,
 
You're welcome, Enjoy...
 
Wes Cowley
Internet: wes@cup.portal.com
  DASNet: [DCI2WC]wcowley
     Bix: wcowley