Error Message: An Exception 00 Has Occurred... (140721)

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:

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.
Type the following commands. Press ENTER after each command:
cd\windows\system\iosubsys ren esdi_506.pdr esdi_506.old
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.