Error message when you start a Windows Vista-based computer after you change the SATA mode of the boot drive.

Problem:
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"

Symptom:
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.

Discussion:
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.

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.