dimar said:
You can move between AHCI and IDE by booting from a separate SATA controller card, then changing the BIOS and drivers. Or the hard way by changing the device ID in registry or something like that, which I've done few times.
There is no need to boot from a separate SATA controller card. Boot Windows into safe mode. Uninstall the PCI drive controller from Device Manager. Reboot the computer into BIOS/UEFI settings. Change the controller mode from PCI to AHCI. Reboot back into Windows Safe Mode. Turn off Safe Mode. Reboot computer into normal Windows.