We help IT Professionals succeed at work.

Check out our new AWS podcast with Certified Expert, Phil Phillips! Listen to "How to Execute a Seamless AWS Migration" on EE or on your favorite podcast platform. Listen Now


Driver Esdi_506.pdr not loading

Boby asked
Medium Priority
Last Modified: 2013-12-29
This driver that is supposed to handle the IDE controllers
for the CD ROM is not loading. I found the following article and followed its suggestions but to no avail.
Can anyone help ?
Troubleshooting MS-DOS Compatibility Mode on Hard Disks
Article ID: Q130179
Revision Date: 12-JUL-1996

The information in this article applies to:

 - Microsoft Windows 95


The Performance tab in System properties shows that one or more of the hard disks in your
computer is using MS-DOS Compatibility mode. MS-DOS compatibility mode may be in use
for either the file system or for virtual memory.


MS-DOS Compatibility mode may be in use for any of the following reasons:

 - An "unsafe" device driver, memory-resident program, or virus

   hooked the INT21h or INT13h chain before Windows 95 loaded.

 - The hard disk controller in your computer was not detected by

   Windows 95.

 - The hard disk controller was removed from the current configuration

   in Device Manager.

 - There is a resource conflict between the hard disk controller and

   another hardware device.

 - The Windows 95 protected-mode driver is missing or damaged.

 - The Windows 95 32-bit protected-mode disk drivers detected an

   unsupportable configuration or incompatible hardware.


To correct the problem, follow these steps:

1. Use the Performance tab in System properties to identify which

   drive is using MS-DOS Compatibility mode and why.

   NOTE: Floppy disk drives and CD-ROM drives operating in MS-DOS

   Compatibility mode cause the Performance tab to display the message

   "Some drives are using MS-DOS compatibility" for the file system,

   but this article applies only to troubleshooting hard disks

   operating in MS-DOS Compatibility mode.

   a. If the driver name listed as causing MS-DOS Compatibility mode

      is MBRINT13.SYS, your computer may be infected with a boot-sector

      virus, or you are running real-mode geometry translation software

      (for an IDE hard disk with more than 1024 cylinders) that is not

      compatible with Windows 95 protected-mode disk drivers.

      For information about real-mode geometry translation software that

      is compatible with Windows 95 protected-mode disk drivers, please

      see the following article in the Microsoft Knowledge Base:

         ARTICLE-ID: Q126855

         TITLE     : Windows 95 Support for Large IDE Hard Disks

      Disk Manager 6.03 is supported in protected mode on hard disks on

      the primary IDE channel and when DriveSpace disk compression is not

      installed. For drives on the secondary IDE channel, Disk Manager 7.0

      or later is required. When using the DriveSpace compression software

      that is included with Microsoft Windows 95 and Microsoft Plus!, Disk

      Manager 7.04 or later must be used. For more information, please see

      the following article in the Microsoft Knowledge Base:

         ARTICLE ID: Q126855

         TITLE     : Windows 95 Support for Large IDE Hard Disks

      For information about detecting and removing boot-sector viruses,

      please see the following articles in the Microsoft Knowledge Base:

         ARTICLE-ID: Q82923

         TITLE     : Methods to Detect a Boot-Sector Virus

         ARTICLE-ID: Q129972

         TITLE     : Description of Computer Viruses

         ARTICLE-ID: Q49500

         TITLE     : List of Anti-Virus Software Vendors

   b. If a driver that is listed in the CONFIG.SYS file is named, contact

      the driver's manufacturer to determine whether there is a version

      of the driver that allows protected-mode access in Windows 95.

   If no driver is listed on the Performance tab, continue with Step 2.

2. Check to make sure that the hard disk controller is listed in Device

   Manager. If it is not listed, install it with the Add New Hardware

   Wizard. If the Wizard does not detect the controller, run the Wizard

   again but do not let the Wizard detect the hardware in your computer.

   Instead, select the controller from the hardware list. If the

   controller is not listed, contact the manufacturer of the hard disk

   controller to determine whether there is a Windows 95 protected-mode

   disk driver or a Windows 3.1 32-bit disk access (FastDisk) driver


   NOTE: If the hard disk controller is listed in Device Manager but has a

   red X over it, it has been removed from the current hardware profile.

   Click Properties for the controller in Device Manager and then click the

   check box corresponding to the current hardware profile under Device


3. If the hard disk controller is listed in Device Manager but has a

   yellow exclamation point over it, there is an IRQ, I/O, DMA, or RAM

   address conflict with another device, the protected-mode driver is

   missing or damaged, or the "Disable all 32-bit protected-mode disk

   drivers" check box is selected in File System properties.

   a. Check to make sure that the "Disable all 32-bit protected-mode disk

      drivers" check box has not been selected on the Troubleshooting tab

      in File System properties. To access this tab, double-click System

      in Control Panel, click the Performance tab, and then click File


   b. Resolve any resource (IRQ, I/O, DMA, or RAM address) conflicts

      with other devices. Consult the controller's documentation for

      information about resource usage and changing resource usage.

   c. Check to make sure that the protected-mode driver is in the

      Windows\SYSTEM\IOSUBSYS directory and is loading properly. To

      determine which driver is providing 32-bit disk access, click

      Properties for the controller in Device Manager and click the Driver

      tab to see which driver files are associated with the controller.

      NOTE: If you are using an IDE, EIDE, or ESDI hard disk controller,

      the Driver tab may not be present when you click Properties for the

      controller in Device Manager. Unless you are using a third-party

      driver, Esdi_506.pdr is the protected-mode driver that is used to

      provide 32-bit disk access for these controllers.

      Restart Windows 95 and press F8 at the "Starting Windows 95"

      message. Select a Logged (/BOOTLOG.TXT) start. Examine the

      just-created BOOTLOG.TXT file to determine if the driver listed

      above is loading properly.

      If the BOOTLOG.TXT file shows an "Init Failure" or "Load Failure"

      message for the driver listed above, proceed with step D. If the

      BOOTLOG.TXT file shows an "INITCOMPLETESUCCESS" message for the

      drive listed above, examine the IOS.LOG file.

      Windows 95 creates an IOS.LOG file in the Windows directory if any

      drives are using MS-DOS Compatibility mode. The first few lines of

      the IOS.LOG file may contain information describing why the

      protected-mode disk driver failed to load. Please have this

      information available if you contact Microsoft Product Support

      Services about this problem.

   d. Make sure the protected-mode driver is not damaged.

      For all ESDI and IDE drives, Windows 95 uses ESDI_506.PDR in

      the IOSUBSYS directory to provide 32-bit disk access. For

      SCSI controllers, Windows 95 uses SCSIPORT.PDR and a "mini-port"

      (.MPD) driver to provide 32-bit disk access.

      Manually extract the appropriate .PDR or .MPD files from the

      Windows 95 disks or CD-ROM, or run Setup and choose the Verify


4. Contact the hard disk controller's manufacturer for information about

   Windows 95 compatibility. You may be able to get protected-mode, 32-bit

   disk access in Windows 95 by using one of the following methods:

    - Disable any enhanced features (such as caching, fast or turbo mode,

      reduced data transfer rates, and so on) on the controller (SCSI, IDE,

      or ESDI) or system BIOS (IDE only).

    - obtain a protected-mode Windows 95 disk driver, or Windows 3.1

      FastDisk driver for the controller.


A real-mode driver is "safe" if its functionality does not exceed the functionality of the
corresponding Windows 95 protected-mode driver. If a real-mode driver is safe, the
protected-mode driver can take over all I/O operations for the corresponding device.
Otherwise, Windows 95 routes all I/O operations through the real-mode driver.

An example of an unsafe driver is a real-mode IDE/ESDI driver that uses dynamic encryption
for security reasons. Since Windows 95 does not provide encryption, Windows 95 does not
allow the protected-mode IDE/ESDI driver to take over the real-mode driver. Any real-mode
driver with functionality on the following list is considered unsafe:

 - Data compression that is not compatible with DoubleSpace

 - Data encryption

 - Disk mirroring

 - Bad sector mapping

 - Fault tolerance (for example, maintenance of ECC correction on a

   separate disk)

 - Vendor-specific IOCTLs

 - Microsoft-defined IOCTLs with vendor-extended features

The safe driver list (the IOS.INI file) is a Windows 95-maintained list of safe drivers. Each
entry in the list identifies a driver or TSR that Windows 95 can take over with the
corresponding protected-mode driver. The safe driver list includes the name of the driver or
TSR. This name should be the same as the name in the CONFIG.SYS or AUTOEXEC.BAT

Windows 95 does not store the version number of the driver or TSR in the list, so it is the
responsibility of the vendor to change the name of the driver if a future version of the driver is
enhanced in a manner that makes the driver unsafe.

By default, the following drivers are considered safe:

 - MS-DOS 5.0-compatible real-mode block device drivers

 - INT 13 monitors (hooks INT 13 for monitoring INT 13 I/O but does not

   access the hardware directly or modify the I/O buffer)

 - INT 13 hooker (hooks INT 13 for altering INT 13 I/O but does not

   access the hardware directly)

 - INT 13 driver (provides INT 13 functionality and directly accesses

   the hardware)

 - ASPI Manager (implements ASPI for MS-DOS specification)

 - CAM Manager (implements MS-DOS
Watch Question

Do you mean you can't see your CD-ROM in DOS?


Hi. Thanks for answering.
No I do see and the CD ROM in DOS. I do not in Windows.
Please have a look at mi question: Problem installing Visual C++.
that is related to this question.

Your dos driver may interfere with the 32 bit driver. Comment out all cd references in config.sys.  If that does not work, go to control panel system performance trouble shoot section. Start with most features disabled, and if it works, reinable them one at a time.

what version of 95 are you using (ie A or  B) and is your CDROM a Primary Slave or
Secondary Master or Slave
Unlock this solution with a free trial preview.
(No credit card required)
Get Preview
Unlock the solution to this question.
Thanks for using Experts Exchange.

Please provide your email to receive a free trial preview!

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.


Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.