Correct me if I'm wrong, You have the LGA 1366 Intel X58 MB?
And the Sata III ports are on a older marvel Controller.
If so you may be better off installing your Agillity III on the Intel Sata II port. You will lose some of the Sequencial read/write performance when compared to using it on an Intel SATA III port, but it will probably perform better over all on the Intel Sata II than on the marvel based SATA III controller.
As Dereck47 indicated, set the Bios to use AHCI (per MB instruction).
.. Disconnect ALL other HDDs, should only have the SSD connected that you want Windows 7 installed on.
..When doing the Install, select CUSTOM mode so that you can first DELETE any and all partitions on the SSD.
.. This will install the default microsoft AHCI driver (msahci - NOT pcide) and create a small 100 mb system partition and align partitons.
.. Once windows has completed install and downloaded updates, Download Intel's latest RST driver (ver 10.6) and install. this will change your driver from msahci -> iaSTor.