I found a pic of the board. It looks to have 4 SATA ports. Are all of the ports controlled by the NVidia chipset, or are 2 of them on another controller (Marvel/SI etc)? I know it's not too old of a system, but are any caps near the southbridge chipset bulged/leaking etc? I had to recap a board a couple months ago that had a similar problem.
I think you went above and beyond with your troubleshooting. I would bet on a fried southbridge/SATA controller.
EDIT: Yes, you should be able to get another SATA controller card as long as you have a free slot. I have never had any troubles with SATA cards, except some compatability problems with optical drives, but that was a few years ago. Never have had problems with cheapie VIA or Silicon Image Chipset controllers.
Edited by dpunisher, 05 August 2011 - 09:59 PM.
I am a retired Ford tech. Next to Fords, any computer is a piece of cake. (The cake, its not a lie)
3770K @4.5, Corsair H100, GTX780, 16gig Samsung, Obsidian 700 (yes there is a 700)