That's how it's supposed to be ... so the SAS BIOS is registering that single drive with the system BIOS, and it's available there as a boot choice?
If yes, then that means you got the SAS "array" set up the way you want it, in single-drive mode. If Windows loads the controller driver, sees the drive, and then refuses to install on it, you might have a screwed up partition table on the drive.
Look for some piece of software that lets you wipe it.