Activate AHCI for newly-installed SSD?

Bought a Samsung 840 EVO 500-bg solid-state drive for a Precision T3500 workstation running 64-bit Win7 Premium. I've

1. cloned the optical hard drive,
2. installed the SSD alongside the HDD,
3. reconfigured the boot order in the BIOS so the system boots from the SSD.

Samsung's "magic" software (a misnomer if there ever was one) tells me that AHCI isn't activated on the SSD. I can't figure out how to activate AHCI. Of the three choices under "Drive" in the configuration utility, the system only boots when set to the default (RAID, no autodetect, no AHCI or whatever the other choice is). Any advice on what I've neglected to do?

thanks...