I had a Windows 7 system working fine in AHCI mode and decided to change the motherboard to another brand. I created an image of the boot drive. I changed the motherboard which runs in IDE mode by default. Restored the image and Windows 7 boots up fine. i decided then to switch to AHCI mode.
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci is set to 0. Changed IDE to AHCI mode in the BIOS. Windows starts but it's stuck at "Starting Windows" for over an hour before I switched off the machine. I booted from the Windows DVD to get into Startup Repair option but it's also stuck in "Starting Windows" screen! I did another try to do the same but without the DVD using F8 to get the boot menu. Same result. So 3 different ways are giving a stuck "Starting Windows". I don't know why AHCI mode is causing Windows not to boot properly.
Any ideas? Is there a way to clean/remove the current AHCI installation from Windows and start a fresh AHCI installation without reinstalling Windows?