Consider the following scenario. In the BIOS setup of a Microsoft Windows 7 or Windows Vista-based computer, you change the Serial Advanced Technology Attachment (SATA) mode of the boot drive to use the either Advanced Host Controller Interface (AHCI) specification or RAID features. You then restart the computer. In this scenario, you receive the following error message:

.STOP 0x0000007B INACCESSABLE_BOOT_DEVICE

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:

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 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.