Error message when you start a Windows Vista-based computer after you change the SATA mode of the boot drive: "STOP 0x0000007B INACCESSABLE_BOOT_DEVICE"
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Article ID : 922976
Last Review : November 13, 2006
Revision : 2.0
Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 (
http://support.microsoft.com/kb/256986/) Description of the Microsoft Windows registry
SYMPTOMS
Consider the following scenario. In the BIOS setup of a Microsoft Windows Vista-based computer, you change the Serial Advanced Technology Attachment (SATA) mode of the boot drive to use the Advanced Host Controller Interface (AHCI) specification. You then restart the computer. In this scenario, you receive the following error message:
STOP 0x0000007B INACCESSABLE_BOOT_DEVICE
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CAUSE
This issue occurs if the AHCI driver (Msahci.sys) in Windows Vista is disabled. This driver must be enabled before you change the SATA mode of the boot drive.
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RESOLUTION
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.To resolve this issue, 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 the following registry subkey:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci
5. In the right pane, 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.
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MORE INFORMATION
During the 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 has been disabled, you must enable the new driver before you change the hardware configuration.
For example, assume that you install Windows Vista 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, visit the following Intel Web site:
http://www.intel.com/technology/serialata/ahci.htm (
http://www.intel.com/technology/serialata/ahci.htm)
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