I just purchased a 2 TB Fantom USB 2.0/eSATA external hard drive. Unfortunately it revealed my oversight when my first custom system was built last summer. I installed Vista Home Premium 64-bit in IDE mode (default in BIOS) instead of the ACHI mode, which would not only provide Native Command Queuing, but also hot plug of external hard drives I need now.

As expected, when I changed the Intel controller to ACHI in the BIOS, the system wouldn't boot any more as expected.

My motherboard is a Gigabyte GA-EX58-UD4P. Both my internal 750 GB WD Black caviar 7200 rpm hard disk drive and my eSATA bridge (providing two eSATA external connections) are connected on three of the six Intel SATA connectors controlled by the ICH10R (southbridge) controller.

The internal hard drive is on SATA0 and eSATA connectors on SATA4 and SATA5. The two SATA connectors controlled by a Gigabyte controller (i.e. GSATA0 and GSATA1) are not used.

The external hard drive driver just installed out of the sudden on my last try as I was writing this post and after I tried to install SATA/RAID drivers while under Windows from Gigabyte website for both Gigabyte and Intel controllers.

Note that Intel setup from MSM/iata_cd.exe gave me an error that my system did not meet the minimum requirement and closed. The new external SATA hard drive is now reported along with the internal hard drive in Device Manager under the IDE/ATA/ATAPI Controllers, with Intel(R) ICH10 Family controller Serial SATA controller.

I am about to upgrade to Windows 7 Home Premium 64-Bit, for which I'd like all SATA drives to operate in AHCI mode. It would allow my external hard drive with an eSATA connection to support hot-plugging and seems beneficial for the internal hard drive too, while multi-tasking.

Enabling the AHCI mode after a Windows Vista install with IDE mode enabled does not seem trivial in the few solutions I read - and a little confusing.


  • Should I enable AHCI mode before (i.e. under Windows Vista) or during the upgrade to Windows 7?

  • If you recommend it is done before, can I enable the ACHI mode without re-installing VISTA? How?

Also, I have multiple partitions for the current Windows Vista install, with Users and Program Data on a different partition that the operating system. The current partition scheme will re-organized and simplified.

  • If you suggest to do it during the Windows 7 Custom clean install, will I still be able to modify this drive partitions scheme (using the Disk Option Advanced mode) in the same custom install session?

  • Since the external drive is operating in IDE Mode with the ICH10R controller, what is the implication that it has no hotplugging capability? Where can it be stopped in the status bar? Is it safe to power it off when the system is running?


Upgrade to Windows 7 first (as it supports newer hardware).

Then 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.

After this you’ll have to restart your computer, go to BIOS, and enable AHCI. When you log in to Windows again, you’ll notice the installation of drivers for AHCI. Another restart will be required to finish the driver installation.

Source: MSKB

You should also check the motherboard manufacturer's website for the latest controller driver.

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  • Thanks for the link and instruction. I did come across this too but dismissed sine I did not notice the error message this solution is fixing. There might be one when a display (blue) blinked at the end of an attempted boot-up when Windows restarted itself. If I understand correctly I could try this under vista too. – Donat Jan 11 '10 at 20:32
  • It worked like a breeze on Vista 64Bit. I did the simple registry change. I copied the files from BootDrv\iMSM\64Bit folder in the Gigabyte install CD onto a usb stick. And after two reboot, voila. Thanks – Donat Jan 12 '10 at 7:28

Considering your other question regarding upgrade versus clean install, I'd go with a full backup of your files and a clean Windows 7 install. Then you can worry about having full control over AHCI.

If you do an upgrade, you might be able to cheat by enabling AHCI in Vista before the upgrade, but I don't know enough to know that this will work.

Theoretically, knowing how the upgrade works (it effectively makes a copy of your personalised data and installed programs and settings, installs a clean version of Windows 7, and then applies said personalisation, programs and settings), it may actually work.

But that's what full system backups are for! :-)

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  • I was able to easily change to AHCI mode in Vista and will start on the right foot for the custom clean install of Windows 7. Thanks. – Donat Jan 12 '10 at 7:33
  • That's good to know. It's a lot easier than figuring out how to enable SMP support in XP after installation :-) – user3463 Jan 12 '10 at 8:30

I would recommend doing a full backup of your Vista files and doing a clean install of Windows 7. If you choose this route make sure you change the disk configuration from IDE to AHCI in your BIOS before beginning the Windows 7 install.

When you begin the Windows install, you have 2 choices with regards to the AHCI drivers:

  1. Go to your motherboard's website and download the "F6" AHCI drivers and copy it to a USB stick or a floppy (if you are still using those). During the initial Win 7 install, you can point to the AHCI drivers on this USB stick/floppy so they canl be installed.

  2. Just let Microsoft install the default AHCI drivers but be sure to upgrade them after the Windows 7 install completes. Usually the motherboard manufacturer will have a version of Intel's Matrix Storage drivers (for RAID and AHCI) on their website for download. If you forget to upgrade the drivers you might find that your internal Hard Drives are being treated like external drives which are removable.

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  • Will Windows 7, when beginning to install, be able to read/access the drive and validate that there is a previous version of Windows to activate after changing mode from IDE to ACHI? – Donat Jan 11 '10 at 20:13
  • I first used the drivers from the motherboard CD. After the first install was complete I downloaded from Intel the latest AHCI Intel storage matrix drivers too. Thanks. – Donat Jan 12 '10 at 7:30

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