Unknown PCI device

I just installed Windows XP Pro on my Dell Dimension 9150. Now when I enter the Device Manager it lists an unknown PCI Device in the Other Devices. I've gone to the drivers and downloads section of this website and downloaded and installed, what I believe to be all the drivers I need, but I still have this "unknown PCI device".

How can I determine what this device is so that I can download the correct driver for it?

Thanks,