DOCUMENT:Q140721  17-DEC-2000  [win95x]
TITLE   :Error Message: An Exception 00 Has Occurred...
PRODUCT :Microsoft Windows 95.x Retail Product
PROD/VER:95
OPER/SYS:
KEYWORDS:win95

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The information in this article applies to:

 - Microsoft Windows 95 
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SYMPTOMS
========

When you start Windows 95, you may receive the following error message on a blue
screen:

   An exception 00 has occurred at 0028:<xxxxxxxx> in VxD ESDI_506(01) +
   00000476. This was called from 0028:<xxxxxxxx> in VxD VPICD(01) +
   <xxxx?>.

CAUSE
=====

Exception 00 is the divide overflow exception. In this situation, the hard disk
controller is reporting a disk geometry of zero sectors per track. This causes
the driver to divide by zero when attempting to communicate with the device.

RESOLUTION
==========

To work around this problem, follow these steps:

1. Start your computer to a command prompt. To do so, restart your computer,
   press the F8 key when you see the "Starting Windows 95" message, and then
   choose Command Prompt Only from the Startup menu.

2. Type the following commands. Press ENTER after each command:

   " cd\windows\system\iosubsys

   ren esdi_506.pdr esdi_506.old " (without the quotation marks)

3. Restart your computer normally.

Renaming the Esdi_506.pdr file causes Windows 95 to use MS-DOS Compatibility mode
for the hard disk, which can result in less than optimal performance.

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

Windows 95 obtains disk geometry information from the Basic Input/Output System
(BIOS) by issuing software interrupt 13h subfunction 08h. The BIOS is supposed
to return the number of sectors per track in the low 5 bits of the CL register,
but it is returning zero instead.

Contact your BIOS manufacturer to see if an updated version of the BIOS is
available.

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Keywords          : win95 
Technology        : kbWin95search kbZNotKeyword3
Version           : 95

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