Change from IDE to AHCI after installing Windows 8

Using regedit, set the key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\storahci
"Error Control": DWORD = 0

and also in the StartOverride tree in storahci. That value needs to be changed to 0:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\storahci\StartOverride
"0": DWORD = 0

After restarting it should work. You can also delete the whole StartOverride block.

Note: If you don't switch to AHCI on the very next boot, the system will create a new StartOverride value (of 3) and you'll have to repeat the process.

I found the solution without having to do a manual registry hack!

1. Click the Restart button with Shift key and follow the prompts for "Advanced Options" through several screens. Eventually, you end up at a screen that tells you upon reboot you will be able to so many things including starting in Safe Mode. The only button will be a "Restart" button on this screen.
2. Reboot. BEFORE Windows starts, enter BIOS setup.
3. Change the SATA mode in BIOS to whatever you would like: IDE, AHCI or RAID(XHD).
4. Boot into Windows. Step 1 configured Windows to ask you what type of boot options you would like to use. #4 is Safe Mode. This will get the proper drivers for the BIOD setting loaded on the system, into memory, and the registry configured correctly for you. No other configuration is required.
5. Reboot Windows in normal mode. Windows will use the configuration that it automatically self-fixed in step 4.

Run msconfig (right click far left bottom corner of desktop then left click run, type msconfig).

Click boot tab, mark safe boot, restart, change to AHCI in BIOS, boot, Windows boots in safe mode.

Run msconfig again, boot tab unmark safe boot, restart PC.

PC works fine. Don't mess with regedit you only need to boot in safe mode to fix this, very simple.