How to enable AHCI in Windows 7 RC after installation

Windows

AHCI (Advanced Host Controller Interface) enables native command queuing and hot-plugging through SATA host controllers (Serial-ATA) for your hard drives. In many scenarios, it enables more efficient multi-tasking. Vista was the first Windows OS to support AHCI out of the box, whereas Windows 7 does the same. But an issue with AHCI is that if you install the OS without enabling AHCI in the BIOS, enabling it after installation will render your OS unusable. This is because Windows disable the AHCI driver since it is not needed during the installation.

There is one way to fix this, although you need to have knowledge of registry editing. The detailed steps from Microsoft are as follows:

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_MACHINESystemCurrentControlSetServicesMsahci
  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. enable ahci in Windows 7

I’ve simplified the steps by Microsoft by exporting the registry key. Just download the following file and run it. You’ll still need to go through the steps of restarting your computer and enabling AHCI in the BIOS.

Hopefully, you’ll find a somewhat noticeable improvement in multitasking, especially if you’re a notebook user. Of course with the variety of PC hardware, experience many vary.

Disclaimer:

Beware, though, you’re responsible on your own for messing around with the registry. This guide comes with no warranties if your computer blows up, gets angry at you, stops working or just shows a Blue Screen of Death.
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243 comments

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  2. I confirm, it does work! just switched from IDE to AHCI, no issues. FYI, this will enable the basic Microsoft AHCI driver.
    Depending on your configuration, it is possible to update this driver with a native AHCI driver from your motherboard manufacturer.
    Last thing I noticed, I had to select my system harddrive to boot properly otherwise my system would hang, although properly selected in the bios.

    Reply

  7. Just an FYI for anyone doing this on Win7 x64, you can’t use the provided .REG file here as it’s setup to point to the x86 version of the driver file. Following the steps listed to make the change manually works fine though

    Reply

  8. Ahhh, thank you very much. This solved my odd issue of Windows 7 shutting down before the log-in screen when using AHCI. :D Now to find out how to get RAID to work…

    P.S. Love the disclaimer. :) How can I not love the nerds with a sense of humour? Wonderful man, just wonderful.

    Reply

  14. Actually this did not work at all on the RTM version. Boot kept failing and I had to use a restore option in order to boot at which point the registry key was set back to the prior setting. And yes, I did change the key properly!

    Reply

    1. Well I messed this up contrary to my claim. My key value was already 0 and I set it to 1 incorrectly. After this was remedied though by a restore, I can boot just fine with my primary sata adapter from Intel in AHCI mode, which it has been from the beginning, but setting my BIOS for the second internal Gigabyte sata controller from IDE to AHCI does still fail to boot but restarts so fast I can’t read the crash screen which is flashed only for an instant. The board is a Gigabyte GA-EP45-UD3P with a P45/ICH10R chipset combination. I guess for some reason, the drivers are not being installed for the Gigabyte sata chipset after changing the BIOS. Registry key is and has been as recommended above. Thanks, Dave

      Reply

  16. Thanks for this, it mostly worked on my RTM version however i'm still having some issues. I can't hot swap sata hard drives and I'm getting errors with the 2 IDE Channel device that's showing up when I open the Devices and Printers screen. I'm guessing this is to do with enabling the AHCI?

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