Sometimes the bios setting for SATA drive is IDE mode by default and we installed windows XP or windows 7 with this setting. Later on, we want to change the bios setting to AHCI to install Mac OS X, we need to re-install windows or fix the registry to run with AHCI mode. We have to do this in windows before the bios is set or we will crash the windows os. Windows 7 or windows XP should have the same registry for msahci. The pictures of the bios here are award bios Gigabyte P55A-UD3 F11. Most of the newer motherboards or computer should have the SATA options AHCI except some old ones don’t have the option. Make sure the AHCI option exists in the bios before changing the registry because if we change the windows registry and the bios doesn’t support AHCI then we will be in trouble.
In msahci click start and change the ide value (3) to ahci (0)- save the registry and reboot.
Click DEL or F2 whichever the case may be while booting to enter bios – the options should be in “Integrated Peripherals” – Change all SATA controllers mode from IDE to AHCI.
Hit F10 to save and exit, the windows will boot in AHCI mode very nicely without any problem.