Unable to Upgrade to Windows 95/98 due to BIOS Boot Sector Virus Protection
by Jan Steunebrink
Last updated on February 27, 1999
Some BIOS manufacturers have put Virus Protection in their products.
Anytime software requests (via the BIOS Harddisk interface Int 13h) to write the Master or DOS Boot Record of drive C:, a Warning is issued to prompt the user if it is safe to continue.
There may be a bootsector virus at work!
When installing Windows 95, Setup needs to write to the DOS Boot Record. The same is true for Windows 98, except when upgrading from Windows 95.
If the BIOS Virus Warning is still Enabled, Setup will fail just after accepting the License agreement.
In addition, there will be no Virus Warning visible because Win95/98 Setup has put the display in graphics mode. This will leave the user guessing what's wrong!
After reboot you will see a message telling you to disable all Virus Protection on your system.
The solution should be simple.
Just Disable the Virus Warning via the CMOS SETUP before installing Windows 95/98.
There are however BIOSs where this is not possible!
I have had reports from the AMI 11/11/92 BIOS but most reports come from specific OEM versions of the Award Modular BIOS v4.50, v4.50G, v4.50PG, and v4.51PG.
For the Award Modular BIOS, I have written a program to restore your control over the BIOS Virus Protection. You can download it here; it is called VIRWARN (5.4 KB ZIPfile).
The program is now at version 1.2 (10/10/97) and comes with a text-file with more information.
VIRWARN is unable to control the Virus Warning feature on non-Award BIOSs, but it will allow you to test for an active Virus Warning on all BIOS brands.
To install Windows 95/98 in case you do not have an Award BIOS or if my Virwarn program is not able to switch the Virus Warning off, you need this workaround.
- Use the undocumented command Setup /ir to prevent Win95/98 setup from writing to the Boot Areas
- Create an Emergency disk during installation (you will be prompted)
- Boot from this disk when Setup has finished
- From the A:\> prompt give the command SYS C: and type 'Y' to accept the modification of the Boot Sector if the Virus Warning pops-up.
- Remove the Emergency disk. You should now be able to boot and run Windows 95/98 from your harddisk.
Some final remarks
The Boot sector Virus Warning feature of the BIOS will only warn you of write
actions to the Master Boot Record or to the DOS Boot Record on your C: drive.
Programs that write to these areas are a/o Boot Sector Viruses, the Setup
program of Operating Systems, the Install program of Disk Manager/EZ-Drive,
disk repair utilities, boot managers, and the DOS programs Fdisk and Format.
The BIOS Virus Warning is only intended to protect these vital disk areas
against the mentioned viruses and you should switch it OFF when
(re-)installing a new operating system or harddisk.
Also use other anti-virus software/hardware to protect your system against
other kinds of viruses!
Note that with Windows 95/98 running the BIOS Virus Warning does not work
because this OS uses its own protected mode diskdriver and the BIOS harddisk
interface is not used anymore (except in safe or compatibility mode).
On the issue of Boot Sector Virus protection in Windows 95 you may like to
read the Microsoft Knowledge Base article:
Any comments? Please send a message to J.Steunebrink@net.HCC.nl
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