According to some docs, the 850 has the CERC SATA 2s, which is a low-end software RAID solution embedded in the motherboard - tied to the onboard SATA ports. Assuming that is the controller, you should have a CTRL-A. If you don't, then there may be an option in the BIOS to enable/disable RAID, which you would not want to do at this point, but if there were such an option, and since it is not a documented (in the 850 manual) option, there may be other undocumented options added via BIOS update. One I would look for is one that might affect how the disks are handled ... some systems have a setting that would change how many ports are available, for example. If there are no relevant BIOS settings that woud affect the second port of the SATA controller, then you might try clearing the NVRAM using the jumpers on the motherboard. The NVRAM (also often called CMOS) contains a list of BIOS settings and devices; if this list becomes corrupt, then devices may not function correctly. Clearing the NVRAM clears this list, returning the BIOS to default settings, and forces the BIOS to rebuild this list. If there are no BIOS settings, and clearing the NVRAM does not help - AND you are sure the disks are hooked up properly - I might have to assume at that point that something is wrong with that second connector.
Do you have any IDE devices connected (like floppy or CD drive)? If so, try disconnecting its cable from the motherboard.