Article ID: 922976 - View products that this article applies to.
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Symptoms

After you use the BIOS setup of a Windows 7-based computer or a Windows Vista-based computer to change the Serial Advanced Technology Attachment (SATA) mode of the boot drive to use either the Advanced Host Controller Interface (AHCI) specification or redundant array of independent disks (RAID) features, you receive the following error message when the computer is restarted: 
STOP 0x0000007B INACCESSABLE_BOOT_DEVICE

Cause

This issue occurs if the disk driver in Windows 7 or Windows Vista is disabled. This driver must be enabled before you change the SATA/RAID mode of the boot drive.

Fix it for me

To resolve this issue automatically, click the Fix this problem link. Then, click Run in the File Download dialog box and follow the steps in this wizard.
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Fix this problem
Microsoft Fix it 50470
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Note This wizard may be only in English. However, the automatic fix also works for other language versions of Windows.

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Note If you are not on the computer that has the problem, you can save the automatic fix to a flash drive or to a CD so that you can run it on the computer that has the problem.

Let me fix it myself

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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:
322756 How to back up and restore the registry in Windows
To resolve this issue yourself, enable the AHCI driver in the registry before you change the SATA mode of the boot drive. To do this, follow these steps:
  1. Exit all Windows-based programs.
  2. Click Start, type regedit in the Start Search box, and then press ENTER.
  3. If you receive the User Account Control dialog box, click Continue.
  4. Locate and then click one of the following registry subkeys:
    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci
    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IastorV
  5. In the pane on the right side, right-click Start in the Name column, and then click Modify.
  6. In the Value data box, type 0, and then click OK.
  7. On the File menu, click Exit to close Registry Editor.

More information

During the Windows 7 or Windows Vista installation process, any unused storage drivers are disabled. This behavior speeds up the operating system's startup process. When you change the boot drive to a driver that is disabled, you must enable the new driver before you change the hardware configuration. 

For example, assume that you install Windows Vista or Windows 7 on a computer that contains a controller that uses the Pciide.sys driver. Later, you change the SATA mode to AHCI. Therefore, the drive must now load the Msahci.sys driver. However, you must enable the Msahci.sys driver before you make this change.

This issue affects only the boot drive. If the drive that you change is not the boot drive, you do not experience this issue.

AHCI provides several features for SATA devices. These include hot plug functionality and power management functionality. For more information about the AHCI specification, go to the following Intel website:
http://www.intel.com/technology/serialata/ahci.htm
Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information. The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

Properties

Article ID: 922976 - Last Review: September 9, 2013 - Revision: 9.0
Applies to
  • Windows Vista Business
  • Windows Vista Enterprise
  • Windows Vista Home Basic
  • Windows Vista Home Premium
  • Windows Vista Starter
  • Windows Vista Ultimate
  • Windows 7 Enterprise
  • Windows 7 Enterprise N
  • Windows 7 Home Basic
  • Windows 7 Home Premium
  • Windows 7 Professional
  • Windows 7 Professional N
  • Windows 7 Starter
  • Windows 7 Starter N
  • Windows 7 Ultimate
  • Windows 7 Ultimate N
Keywords: 
kbtshoot kbhardware kberrmsg kbexpertiseinter kbprb kbfixme kbmsifixme KB922976

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