With my mobo, asus p7p55d - (regular, not pro, not evo, not e), it has a weird chipset issue for raid where it only allows (apparently: newegg reviews) to have an all or nothing raid function.
This statement is incorrect for an ICHxR. Even an old P5W DH Deluxe doesn't have such an issue. All ports will be in RAID mode, but that doesn't mean that all devices have to be RAID members. I strongly recommend that you configure the controller in RAID mode before installing the OS.