Change from IDE to AHCI without crashing Windows 7

By Cèbe, . Permalink Windows 7

I noticed my system was using IDE (and not AHCI) and it is highly recommended to use AHCI for SSD drives.

Ubuntu won't complain if mode is switched from one to the other. However, Windows 7 is a bit more picky as the AHCI driver is disabled by default (to gain a few seconds at startup) and thus won't boot in AHCI mode. Here is how to change from IDE to AHCI without crashing Windows 7:

You start with step 1 while you are still in Windows in IDE mode.

  1. Run the Registry Editor (regedit.exe)
  2. Navigate to Registry Key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci
  3. Set the "Start" value to 0 (zero)
  4. Navigate to Registry Key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Pciide
  5. Set the "Start" value to 0 (zero)
  6. Shut down
  7. Start up again, but before Windows boots go into the BIOS configuration screens and change the disk mode to "AHCI". Save the new BIOS configuration and restart so that Windows boots.

There is also a Microsoft FixIt tool: http://support.microsoft.com/kb/922976

(In the end, it turned out AHCI was already enabled for Windows. I reset the BIOS settings a while ago because some USB ports were stuck in USB 1.1 and didn't set the BIOS properly after that).

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