Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!gatech!udel!princeton!siemens!jrv
From: jrv@siemens.UUCP (James R Vallino)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Removing non-DOS partition
Message-ID: <527@siemens.UUCP>
Date: 25 Apr 88 13:43:32 GMT
References: <290@unisv.UUCP> <1479@edison.GE.COM>
Reply-To: jrv@siemens.siemens.com (James R Vallino)
Organization: Siemens RTL, Princeton, NJ
Lines: 38

The structure of the partition table is shown in the IBM Technical Reference.
The table is stored in the first sector of the hard disk.
Removing an unwanted partition is a fairly simple process using DEBUG.
Here is the procedure which I used when I had the same type of problem:

1. Read the boot record/partition table into memory. Assemble the following
    program in memory using DEBUG and run it to the nop:

	mov ah,2	    ;ah = 2 read disk, 3 write disk
	mov dl,80	    ;dl = 80 - 81 for first or second hard disk
	mov dh,0	    ;head 0
	mov cx,1	    ;cylinder 0  sector 1
	mov al,1	    ;read/write 1 sector
	mov bx,200	    ;es:bx => data buffer for read/write operations
	int 13		    ;do the disk operation
	nop		    ;run program to this point

2. The partition table will start at offset 3be if the data buffer is 200 as
    above. Data for the four partitions start at:

	3be	partition 1 (offset 1be in sector)
	3ce	partition 2 (       1ce          )
	3de	partition 3 (       1de          )
	3ee	partition 4 (       1ee          )
	3fe     55 AA  (these two bytes must end the boot record)

   To wipe a partition off the face of the disk zero all the bytes in its
   area of the partition table.

3. After modifying the partition table change the program above so that AH is
    set to 3 (write disk), hold your breath, and run it again to write the
    modified partition table to disk.



-- 
Jim Vallino	Siemens Research and Technology Lab.,Princeton, NJ
CSNET: jrv@siemens.siemens.com
UUCP: {ihnp4,philabs,seismo}!princeton!siemens!jrv