EDIT: I can only mark one answer as the correct one but the actual solution was a combination of two comments (updating the BIOS to A15 AND installing the Sigmatel audio drivers).

I have a Dell Latitude D830 laptop that is running Windows 7 Enterprise x64. I connect to a docking station during the day with multiple monitors, a keyboard and a mouse. Everything runs with no problems including most of the docking station ports (usb, monitors, etc.) However, the sound port from the docking station does not work since the upgrade to Windows-7. Even with the laptop plugged in, the sound always comes out of the laptop, not the headphones plugged into the docking station.

Here's what I've tried:

I've seen other issues like via Google this that seem to be mostly unanswered. I found one or two that referenced using the Vista x64 drivers, especially the Nvidia drivers.

I do not have an Nvidia chipset but I've reinstalled the sound drivers and that has not helped.

I don't have a support contract and considering the cost is usually high to call Dell, that's not an option.

Dell's forums are pretty much a wasteland and I've found no help there.

Since this is a docking station I thought I might need to try the SATA or Intel chipset drivers from the dell site instead, however I'm not really sure and I need to work on this laptop in the meantime. I can't really afford the downtime to experiment with random drivers all day in case they turn out to be incompatible (Dell still hasn't added Windows 7 to their support site as far as I can tell).

Does anyone have any other ideas? Has anyone had this issue and solved it? If so, how? Thanks in advance for your help.