Your BIOS seems outdated. Try installing the latest MSI BIOS for your board. According to what I've read, only newer BIOS versions support AHCI.
MoBo: Gigabyte EP45-DS3R (F11e)
Cpu: Intel Q9550 @ 2.83GHz
Gfx: Palit Geforce 9500 GT 1GB passive
Mem: 4GB OCZ Reaper PC800
Snd: TerraTec Audiosystem EWX 24/96
SCSI: Adaptec AHA-2940UW (not working under Mac OS X)
Hdd 1: 1TB Seagate ST31000528AS
Hdd 2: 1TB Seagate ST31000528AS
Dvd: LG GSA-4167B (IDE)
Cd: Plextor PlexWriter Premium (IDE)
MacOS: AsereBLN Booter 1.1.9 (Chameleon 2.0 RC4/PCEFI10.5 based) & OS X 10.6.5
I cannot find your specific motherboard, guess it is a P33, does it have another name? But as suggested by the Great Gatsby try and change your bios, then AHCI mode is found under SATA controller in AMI BIOS.
MB:Asus Z77 Sabertooth
CPU:Intel i7-3770K
HD4000 Graphics
RAM:16 GB DDR3 Corsair 1600
To be a bit more specific about this: I don't know your board and I have no idea how MSI numbers its BIOS versions. However, when I type in 'MS-7360' into this page's search form, I am re-directed to this page, according to which it's either a G33 Neo or a P35 Neo.
The post I linked above is about a P35 Neo and states that it only supports AHCI beginning with a certain firmware, which is said to be firmware 1.10 of november 11, 2008. I have no ways and means to verifiy this, of course, I just wanted to tell you that it is what I found when I googled.Be also aware that one poster in this thread says the firmware is quite buggy, so try it with caution.
MoBo: Gigabyte EP45-DS3R (F11e)
Cpu: Intel Q9550 @ 2.83GHz
Gfx: Palit Geforce 9500 GT 1GB passive
Mem: 4GB OCZ Reaper PC800
Snd: TerraTec Audiosystem EWX 24/96
SCSI: Adaptec AHA-2940UW (not working under Mac OS X)
Hdd 1: 1TB Seagate ST31000528AS
Hdd 2: 1TB Seagate ST31000528AS
Dvd: LG GSA-4167B (IDE)
Cd: Plextor PlexWriter Premium (IDE)
MacOS: AsereBLN Booter 1.1.9 (Chameleon 2.0 RC4/PCEFI10.5 based) & OS X 10.6.5