Advanced Host Controller Interface (AHCI) enables support for hot-plugging and native command queuing, but only the newest operating systems supports this interface. Therefore one have enable it explicitly in the motherboard BIOS.
If already having installed Windows Vista/7 without ACHI enabled, then Windows has automatically disabled its AHCI driver to improve the boot time (not loading unnecessary harddisk controller drivers). Therefore one have to activate the AHCI driver before enabling ACHI support in the motherboard BIOS. Open the registry editor and set the following DWORD value:
Note if changing to AHCI mode in motherboard BIOS and the Windows operating system doesn't have a AHCI enabled driver, then it will give a blue screen of death (BSOD) with STOP 0x0000007B INACCESSABLE_BOOT_DEVICE.
[HKEY_LOCAL_MACHINE \System \CurrentControlSet \Services \Msahci]
Start = 0
Note it can be a good idea to get the latest AHCI driver from the motherboard chipset manufacture, instead of using the default AHCI driver included with Microsoft Windows.
Note enabling AHCI might stop SMART data from working. This is apparently a driver issue, and doesn't happen if using Microsoft Windows default driver.
More Info MS KB922976