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1993-06-22
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======================================================================
Microsoft(R) Product Support Services Application Note (Text File)
PD0321: REMOVING NON-DOS PARTITIONS WITH DEBUG
======================================================================
Revision Date: 4/93
No Disk Included
The following information applies to Microsoft MS-DOS(R) versions 3.2,
3.21, 3.3, 4.0, 4.01, 5.0, and 6.0.
--------------------------------------------------------------------
| INFORMATION PROVIDED IN THIS DOCUMENT AND ANY SOFTWARE THAT MAY |
| ACCOMPANY THIS DOCUMENT (collectively referred to as an |
| Application Note) IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY |
| KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO |
| THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A |
| PARTICULAR PURPOSE. The user assumes the entire risk as to the |
| accuracy and the use of this Application Note. This Application |
| Note may be copied and distributed subject to the following |
| conditions: 1) All text must be copied without modification and |
| all pages must be included; 2) If software is included, all files |
| on the disk(s) must be copied without modification [the MS-DOS(R) |
| utility DISKCOPY is appropriate for this purpose]; 3) All |
| components of this Application Note must be distributed together; |
| and 4) This Application Note may not be distributed for profit. |
| |
| Copyright 1990-1993 Microsoft Corporation. All Rights Reserved. |
| Microsoft and MS-DOS are registered trademarks and Windows |
| is a trademark of Microsoft Corporation. |
--------------------------------------------------------------------
INTRODUCTION
============
There are currently several different versions of MS-DOS in the
personal-computer environment, both in the OEM-licensed versions and
in the Microsoft packaged-product versions. The hard-disk-management
capabilities of MS-DOS vary from one version to another. For example,
MS-DOS versions 3.2 and 3.21 can address a single hard-disk partition
of up to 32 megabytes (MB); MS-DOS version 3.3 can address multiple
hard-disk partitions, with a primary DOS partition of up to 32 MB and
an extended DOS partition containing logical drives of up to 32 MB
each; and MS-DOS versions 4.0, 4.01, 5.0, and 6.0 can address multiple
hard-disk partitions with sizes up to 2 gigabytes (GB).
For those using versions of MS-DOS that have lesser levels of hard-
disk support, such as MS-DOS versions 3.2 and 3.21, there are a number
of third-party hard-disk-management software packages that allow
MS-DOS to access multiple partitions and/or partitions in excess of 32
MB. However, these third-party packages may use non-DOS constructs to
assist in managing the hard disk, possibly including non-DOS
partitions. These non-DOS constructs can cause problems when you
upgrade to later versions of MS-DOS because versions of MS-DOS earlier
than 5.0 assume that non-DOS constructs are owned by another operating
system and, therefore, do not use, delete, or change non-DOS
partitions or other non-DOS constructs in any way.
WARNING: Some computers require the use of third-party hard-disk-
partitioning software because the system ROM BIOS does not fully
support the drive parameters of the hard disk that is being used or
because the hard disk has more than 1024 data cylinders. If you are
unsure if your system supports your hard disk, consult your hardware
manufacturer or the manufacturer of your partitioning software
before proceeding.
USING DEBUG TO REMOVE A NON-DOS PARTITION
=========================================
The Debug script below, used with the MS-DOS Debug program, deletes
non-DOS partitions when you upgrade to a new version of MS-DOS,
enabling the entire hard disk to be used by MS-DOS. It does so,
however, by clearing out the entire partition table on the hard disk,
which results in the DELETION OF ALL PARTITIONS on the hard disk. You
need to use this method if your current version of MS-DOS cannot
delete non-DOS partitions.
WARNING: Because all data on your hard disk will be destroyed by
this procedure, you must back up your hard disk before using this
Debug script.
There are two ways to use the following Debug script:
- Run Debug and type the Debug commands from the center column of
Table 1 at the corresponding Debug prompt. (The left column of the
table shows the prompts that are displayed by Debug. You do not
need to type the comments in the right column.)
-or-
- Type the command in the center column of Table 1 into a file using
a text editor such as MS-DOS Editor and then use input redirection
to feed the resulting file into Debug. For example, if you typed
the commands into a file called HDPART.SCR, you would clear your
partition table by typing the following at the MS-DOS command
prompt and then pressing ENTER:
debug < hdpart.scr
Table 1: Debug Script to Erase Hard-Disk Partition Table
------------------------------------------------------------
Debug Enter Debug Comments
Prompts Commands
------------------------------------------------------------
- A 100 Assemble from CS:0100
nnnn:010 INT 13 Call interrupt 13
0
nnnn:010 press the (nnnn in the segment address).
2 ENTER key
- RAX Replace AX register.
AX 0000
: 0301 Write on sector.
- RBX Replace BX register.
BX 0000
: 0200 Start from ES:200
- F 200 L 200 0 We want to write zeros.
- RCX Replace CX register.
CX 0000
: 0001 Cylinder, 0, sector 1.
- RDX Replace DX register.
DX 0000
: 0080 First physical hard disk, head
0. (Substitute 0081 for this
entry if clearing the table on
the second physical hard disk,
0082 if clearing the third
physical hard disk, and so
forth).
- P Proceed (Debug will display
several lines of information).
- Q Quit Debug.
This script completely clears the partition table on your hard disk,
preparing the hard disk for repartitioning using the MS-DOS Fdisk
program. (When you run Fdisk for the first time after using this
procedure and before reinstalling MS-DOS, the message "No partitions
defined" should be displayed if the partition deletion procedure was
successful.) For more information about using Fdisk, see the
"Microsoft MS-DOS User's Guide and Reference" for version 3.2, 3.21,
3.3, 4.0, 4.01, or 5.0, or the "Microsoft MS-DOS User's Guide" for
version 6.0.
Non-DOS partitions on your hard disk are also erased if you perform a
low-level format. Consult your hardware manufacturer for specific
instructions on performing a low-level format on your hard disk.
WARNING: Performing a low-level format will completely erase all
data on your hard disk, including all defined partitions.