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The information in this article applies to:

    Microsoft Windows 95
    Microsoft Windows 95 OEM Service Release versions 2, 2.1
    Microsoft Windows 98

IMPORTANT: This article contains information about editing the
registry. Before you edit the registry, you should first make a backup
copy of the registry files (System.dat and User.dat). Both are hidden
files in the Windows folder.

SYMPTOMS

If your computer contains a PCI-IDE hard disk controller that employs
serialization between the two IDE channels, you may experience the
following problems:
 

•     32-bit file system access and 32-bit virtual memory are not available.
•     Device Manager displays an exclamation point in a yellow circle for the primary  and secondary IDE channels.

Removing and reinstalling the hard disk controller does not resolve the problem.

CAUSE

The protected-mode driver for the hard disk controller was not
properly initialized when you started Windows previously. When this
occurs, a NOIDE entry is placed in the registry, preventing Windows
from making future attempts to initialize the protected-mode driver.

RESOLUTION

NOTE: The purpose of the registry key mentioned in the
RESOLUTION section of this article is to prevent data corruption.
Before you change this key, Microsoft recommends you perform the
troubleshooting steps listed in the following Microsoft Knowledge
Base article:

   ARTICLE-ID: Q130179
   TITLE     : Troubleshooting MS-DOS Compatibility Mode on Hard Disks.

WARNING: Using Registry Editor incorrectly can cause serious
problems that may require you to reinstall Windows 95. Microsoft
cannot guarantee that problems resulting from the incorrect use of
Registry Editor can be solved. Use Registry Editor at your own risk.

NOTE: For information about how to edit the registry, view the
Changing Keys And Values online Help topic in Registry Editor
(Regedit.exe). Note that you should make a backup copy of the
registry files (System.dat and User.dat) before you edit the registry.

To cause Windows to attempt to reinitialize the protected-mode IDE
driver, remove the NOIDE entry from the following registry key:

   HKEY_LOCAL_MACHINE\SYSTEM\CURRENTCONTROLSET\SERVICES\VXD\IOS

If you are using Windows 98, navigate to the Tools\Mtsutil folder on
the Windows 98 CD-ROM, right-click the Noide.inf file, and then click
Install. This should remove a NOIDE entry if it exists. After you use this
file, restart your computer.

After you update the registry, restart Windows. Windows will then
attempt to initialize the protected-mode driver for the controller. If no
problems are encountered, the file system and virtual memory will
operate in 32-bit mode, and Device Manager will not display an
exclamation point in a yellow circle for the IDE channels.

If the protected-mode driver is not initialized properly, an error
message will be displayed and the NOIDE registry entry will be
re-created. Windows will use the MS-DOS compatibility mode file
system the next time you start the computer.

MORE INFORMATION

This problem can occur with an IDE controller that requires
serialization between the primary and secondary IDE channels. The
protected-mode drivers for these IDE controllers can fail to be
initialized if one of the following situations occurs:

    One IDE channel has a supported hard disk, and the second
    channel has a CD-ROM or other type of drive that requires
    real-mode drivers to be loaded. Because of the serialization
    between the two IDE channels, it is impossible to access the
    hard disk in protected mode and use the other device in real
    mode. This causes the protected-mode driver to fail
    initialization, and the NOIDE switch is placed in the registry to
    prevent future errors. Both disk devices then operate in real
    mode.
    The driver for the IDE controller is manually removed from
    Device Manager and then reinstalled, or the protected-mode
    driver is disabled and then re-enabled. Some PCI controller
    drivers are not designed for dynamic enabling and disabling,
    and can cause the protected-mode driver to fail initialization.

The Windows device drivers for the following controllers are known to
exhibit this behavior:

    CMD PCI-0640 PCI-IDE controller
    Standard Dual PCI-IDE controller
    Opti Dual PCI-IDE controller

Other PCI-IDE controllers that use serialization between the IDE
channels may also exhibit this behavior.

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