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msahci.sys missing in Windows 8 64-bit

 Having installed a SSD as the boot disk, I tried to switch from IDE to AHCI in the BIOS (eVGA x58FTW3 mainboard) and applied a registry fix found on-line. Now I can't boot from the new drive. The error message indicates corrupt or missing msahci.sys. I went back to my HDD boot disc and the computer started without a problem. I switched it back to IDE.

The file msahci.sys does not appear on either drive, old or new. The drive contents are identical -- except for that registry change.
I haven't found any official documentation specific to Windows 8.
If need be, I could remigrate my HDD contents to the SDD. Still, I'd like to be able to activate AHCI for the SDD drive.
You may need to switch to AHCI BEFORE installing Win 8 on the SSD. Sometimes switching afterwards can be a bit tricky, it not impossible...
My msahci.sys is located in System32Drivers, but I have no idea how it got there...
Check your specs closely for your SSD and make sure it supports AHCI... It most likely does, but I have a Vertex 4 that will not work in IDE Mode, so I suppose that it is possible some brands won't work in AHCI Mode.