My 32" Samsung TV disabled analog sound input when HDMI sound is detected. Unfortunatly, new nVidia cards enable audio through HDMI even when SPDIF isn't connected. I still wanted to use my TV and my X-Fi, so I had to find a solution. My TV doesn't have an option to use another sound source if it detects an HDMI audio signal. After failing to try and disable HDMI audio through a nVidia driver hack, I decided to find a way to get SPDIF to work. I looked and looked until I found this diagram.
I took a simple two pin cable and attached it to SPDIF0 Out and the GND next to it. Thats pin 9 and 7. I then connected the ground to the pin closest to the PCI-E power connectors on my GTX 280 and the SPDIF0 Out to the other one. I then booted up my PC and the sound worked! So after a few hours of frustration I decided to make this post for those out there who may not know that you can connect an X-Fi to the SPDIF input on the newer nVidia cards.