MikersSU

Sorry for the double post but here's some info I found in Wiki on AHCI.

* Enabling AHCI in a system BIOS will spawn a 0x7B BSoD STOP error on installations of Windows XP where AHCI/RAID drivers for that system's chipset are not installed. Switching to AHCI requires installing new drivers before changing BIOS settings. Some later versions of Windows XP Service Pack 2 include limited AHCI/SATA support

* When attempting to install Microsoft Windows XP or a previous version on an AHCI-enabled system will cause the setup to fail with the error message "set up could not detect hard disk drive...". This problem can only be corrected by using a floppy disk with the appropriate drivers or by slipstreaming the appropriate drivers into the Windows XP installation CD.

* Enabling AHCI in a system BIOS with Windows Vista already installed will result in a BSoD if SATA has been running in IDE mode during Vista's installation. Before enabling AHCI in the BIOS, users must first follow the instructions found at Microsoft Knowledge Base article 922976 (currently unavailable in English, see this workaround using babelfish).

* Enabling AHCI or receiving a system with AHCI enable, will cause EPHD (Encryption Plus Hard Drive from PC Guardian) to error out when attempting to Hibernate out of Windows OS (such as Windows XP). The major aspect of this issue is that it can NOT be changed without reimaging/re-installing the entire system. There may be a root level fix not apparant on new (Circa April 2007) HP Compaq NC8430 laptops.

* Enabling AHCI in a system BIOS on installations of Windows XP or Windows Vista, will cause SATA Optical drives to disappear. A Hotfix for Windows Vista is available. SATA optical drives are not available after you start a Windows Vista-based computer Microsoft Knowledge Base article

Guess my experience is the norm.