X58 Super computer sound problem

Hi,

Im trying to connect my pc to my tv using hdmi. I need to use a spdif cable with the nvida 9800gx 2 to chanel the sound to the tv, and ive pluged it in on the spdif slot on my motherboard several ways with no result the spdif cable has a 2 pin conector red/black wires but the motherboard spdif slot has 3 pins.

These are 2 diagrams from the x58 super computer manual

Diagram in - onboard headers and connectors section.

Pin 1 - +5v
Pin 2 - Empty gap
Pin 3 - Spdif out
Pin 4 - Ground

Diagram in - pin header easy instalation guide.

Pin 1 - +5v
Pin 2 - Spdif
Pin 3 - Empty slot
Pin 4 - Ground

These diagrams are confusing as it is not clear witch diagram is correct.
Witch two connectors are required for it th work.

I can only connect the spdif cable to two of these, with the cable ive got. Do i need a new cable to fit all three pins. or can i fit it to two of them to get it work.

If i need to connect it to two of them can you tell me what i need to do next to get the sound working properly.

Thanks War994.

SYSTEM: Vista 64 bit ultra.
CPU I7 920
CPU COOLER: THERMALRIGHT ULTRA 120 EXTREME + 120MM FAN.
PSU: THERMALTAKE 1500W
MOTHERBOARD: ASROCK X58 SUPERCOMPUTER
MEMORY: CORSAIR DOMINATOR 6GB DDR3 1600MHZ
SOLID STATE HARD DRIVE: OCZ CORE SERIES V2 60GB AS BOOT DRIVE.
HARD DRIVE: 300GB WD VELOCIERAPTOR.
GPU: NVIDIA 9800X2.
CD/DVD/BLURAY DRIVE.