If your computer contains a Peripheral Component Interconnect (PCI) Integrated Drive Electronics (IDE) hard disk controller that employs serialization between the two IDE channels, you may experience the following behaviors:

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

If you uninstall and then reinstall the hard disk controller, this behavior is not resolved.

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This behavior can occur if the protected-mode driver for the hard disk controller is not properly initialized when you start Windows. When this occurs, a NOIDE value is placed in the registry which prevents Windows from making future attempts to initialize the protected-mode driver.

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Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
NOTE: The purpose of the registry value that is mentioned in this section is to prevent damaged data. Before you modify this registry value, it is recommended that you perform the troubleshooting steps in the following Microsoft Knowledge Base article:

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All Versions

To cause Windows to attempt to reinitialize the protected-mode IDE driver:

1.	Click Start, click Run, type regedit in the Open box, and then press ENTER.
2.	Locate and click the following registry key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\IOS
3.	In the right pane, right-click the NOIDE value, and then click Delete.
4.	Quit Registry Editor.

After you update the registry, restart Windows. Windows attempts to initialize the protected-mode driver for the controller. If Windows can initialize the protected-mode driver for the controller, the file system and virtual memory operate in 32-bit mode and Device Manager does not display an exclamation point in a yellow circle for the IDE channels.

If the protected-mode driver is not initialized properly, you receive an error message and the NOIDE value is re-created. Windows uses the MS-DOS Compatibility mode file system the next time that you start the computer.

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Windows 98 Only

If you are running Windows 98 on your computer, locate the Tools\Mtsutil folder on the Windows 98 CD-ROM, right-click the Noide.inf file, and then click Install. When you do this, the NOIDE value is deleted if it exists. After you use this file, restart your computer.

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This issue can occur if your computer has an IDE controller that requires serialization between the primary and secondary IDE channels. The protected-mode drivers for these IDE controllers may not be initialized if one of the following situations occurs:

•

If one IDE channel has a supported hard disk, and the second channel has a CD-ROM or another type of drive that requires Real-mode drivers. Because there must be serialization between the two IDE channels, Windows cannot access the hard disk in Protected mode and use the other device in Real mode. When this occurs, the Protected-mode driver is not initialized and the NOIDE switch is placed in the registry to prevent future errors. Both disk devices can then operate in Real mode. -or-

•

If you manually remove the driver for the IDE controller from Device Manager and then reinstall it, or if you disable and then re-enable the protected-mode driver. Some PCI controller drivers are not designed for dynamic enabling and disabling, and can cause the Protected-mode driver to not initialize properly.

The Windows device drivers for the following controllers may cause this behavior:

•	CMD PCI-0640 PCI-IDE controller
•	Standard Dual PCI-IDE controller
•	Opti Dual PCI-IDE controller
•	Intel 82371 AB/EB Pci Bus Master IDE Controller
•	Ali M5229 PCI Busmaster IDE Controller

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

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