Can't get sound over audio on my HTPC

[sm8000]

My HTPC has an old nForce2 motherboard with Soundstorm. If I use digital via optical (STB) or coax (PC), I get sound just fine.

However when playing streaming videos, obviously I only get sound thru the front speakers. I decided to wire my speakers up with analog to see if I could get sound through all my speakers (Logitech Z-5500s).

I connected the analog cables to the control pod, then to the PC. I connected the colors like this:

(cables - PC)
Green - Green
Black - Blue
Orange - Pink

I also checked the boxes saying Line-In is Center and Mic is Rear, or however it's worded in Volume Control -> Advanced.

When I run the NvMixer utility and do the speaker test, I hear the white noise when it tests digital, but not when it tests analog. I also get no sound thru Winamp, WMP, etc.

Any ideas? I'm using Soundstorm driver 4.62 (latest I can find on nvidia.com), the motherboard is an MSI K7N2G-ILSR with the latest BIOS, and the OS is WinXP MCE 2005 SP3.