I'm not sure if this mobo is the same but...
Sometimes there is an extra SATA RAID "bios" which will come up just after or during the POST. It may say something like "Press ALT-F" or similiar.
This mini "bios" usually controls the 3rd-party raid/sata chip. If its there you may have to enable a single drive raid to get it to work.
I would have hoped that an A8N32-SLI would have done away with this kind of SATA system but its worth having a look.
If the mobo does have these settings it might be easier to move the sata cable to another connector on the motherboard, maybe in the other block of connectors.
P.S. I looked at a picture of your mainboard, are you plugging the sata cable into one of the 4 black connectors, or the lonely red one. It should be in the black ones as I understand.