There was no specific reason given. This was on a Linux forum, so maybe it has to do with that system. Although it hasn't caused me any problems as far as I can tell, so still I don't know why. Maybe he figured it had to do with another problem I was having, but that's since been solved.
I suppose I'll let this thread die. Should I mark it as Solved even if I wasn't technically able to switch (the point of this thread)?
I don't know. If you mark it solved then someone coming along later looking for an answer to do the same thing will not find that answer here. I think it should be marked solved if it is solved.
FYI, there is a solution which addresses directly and simply the switch from RAID to AHCI as indicated in the topic, without a reinstallation of W7.
If you go to the page Error message occurs after you change the SATA mode of the boot drive, you’ll find Microsoft Fix it 50470. Just execute this module under Windows 7, reboot, switch RAID to AHCI in the BIOS and Windows 7 will then boot with no BSOD.
Nothing else is required, just another reboot.
I have a related post. My new Dell Precision T3610 came with BIOS in RAID SATA mode. The msachi start value was set to 3 which confuses me. I switched BIOS to SATA AHCI expecting a BSOD. It booted fine and a check of the registry shows following start values: msachi = 3, IastorV = 3, Pcide = 0, Atapi = 0. Intel RST says everything is fine and I am enjoying advanced SATA features. It all seems contrary to what I've read here and in Microsoft KB.
Hello paradisca1. Welcome to the forum.
That is quite strange. I certainly can't explain it.
Does that system use the new UEFI bios?
Thanks for your attention.
It has the uefi option in the BIOS setup but I've left it at the default Legacy (MBR) mode.
If you install in IDE mode and switch to AHCI, it will BSOD because the install was in IDE mode, so the OS does not include the AHCI drivers. If you install in Raid mode and install Intel rapid storage technology (Intel's Raid driver) the IRST includes the IaStor AHCI driver. So, when you switched the mode to AHCI, it already had the AHCI drivers, so it booted. The fix to change from IDE to AHCI is a registry change in an attempt to force the OS to install the AHCI drivers. You already had them. That's the way I understand it anyway. IRST is the only way to get the IaStor.sys driver that I know of.
Thank you, essenbe. So if I now switch BIOS to SATA ATA it should boot in ATA mode, right? And if I then go into the registry I should find HKLM\SYSTEM\Services\msahci with a value = 3, right? And if I now set that value to 0 and reenter the BIOS and set the SATA mode back to AHCI and boot it should reinstall msahci.sys and then reboot into AHCI mode, right? I hope I have it right.
I understood you to say that you had changed it to AHCI in bios and it booted. Was I wrong? If I was right, you are already in AHCI mode, or should be. Go to device manager and post a screenshot of an expanded IDE ATA/ATAPI Controllers. (Screenshots and Files - Upload and Post in Seven Forums).
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