Switching from IDE to ACHI really should be done in the BIOS before installing the OS. Doing so after the fact creates some problems. That's not to say it can't be done. You might find this - http://superuser.com/questions/471102/change-from-ide-to-ahci-after-installing-windows-8
- an interesting read that may help solve your problem. There are a couple of suggestions as to what to try and what to do. If you choose to edit the registry you need to do so with caution and make sure you make a backup copy of the registry and store it on a flash drive or other external device.