MS-DOS 6 or 6.2 Setup and ROM-Based Virus Detection
PSS ID Number: Q104910
Article last modified on 11-01-1993
PSS database name: O_MSDOS

6.00 6.20

MS-DOS


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The information in this article applies to:

 - Microsoft MS-DOS operating system versions 6.0 and 6.2
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SYMPTOMS
========

The MS-DOS 6 or 6.2 Setup program may fail during creation of the
Uninstall disk after the FAT.DAT file is written to the Uninstall
disk.

NOTE: You may also see this error when you use Fdisk to rewrite the
master boot record (MBR).

CAUSE
=====

The ROM BIOS in many computers can be configured to automatically scan
the boot sector for viruses. ROM BIOS chip sets that are known to
provide this feature include various versions of the following:

 - American Megatrends International (AMI) BIOS dated 1992 and 1993

 - Award BIOS version 3.2 or later

 - Microid Research BIOS (in particular, the versions in Brother models
   BCN3-386DX/33C and BCN5-386DX/33C)

If the boot sector virus-detection feature is enabled, the MS-DOS 6 or
6.2 Setup program fails when it attempts to write to the boot sector.
The BIOS may then report an error message stating that a possible
virus has been detected. The specific error message for each computer
is dependent on the BIOS, however, it will probably be similar to the
following:

 - Virus-protection software has been activated--system halted
   (MR BIOS)

-or-

 - Boot sector write error!
   Possible virus!
   Do you want to continue Y/N?
   (AMI BIOS)

-or-

 - Illegal write to boot sector attempted, Y to continue, A to abort
   (Award BIOS)

WORKAROUND
==========

To work around this problem, run the CMOS setup for the computer and
disable the option to protect the boot sector from viruses. After this
option has been disabled, you can restart your computer and safely run
MS-DOS 6 Setup. The boot sector virus-detection feature can then be
reenabled after installation is complete.

MORE INFORMATION
================

The products included here are manufactured by vendors independent of
Microsoft; we make no warranty, implied or otherwise, regarding these
products' performance or reliability.

Additional reference words: 5.00 6.00 6.20 systems beep beeps errmsg
mister 3rdparty hardware format stop lock

Copyright Microsoft Corporation 1993.