The Agility III can be a little picky on which systems it works with. Visit the OCZ forums and look at the costumer feed back. I bought two of them, never again, It would not install on a New sandbridge notebook even with AHCI inabled. Ended up going with the Curcial M4 which worked fine.
With OCZ Sata III SSDs, AHCI is recommended (also works with intel Raid selected), and for some operation such as updating the firmware and doing a secure erase ahci is required.