Yes, I've tried reading both my Motherboard and Chassis manuals, but none of them isn't help. It's a HAF 912 Advanced chassis. I did however found the AC97 header, can i plug in the HD Audio to a AC97 header? Since the HD Audio plug is daisy chained off the end of AC97.
You can't plug the AC97 connector in the HD header. The pc case's HD connector should fit correctly.