From a bit of Googling around, I'm pretty sure that the D4810B is what's called a softmodem or winmodem. Softmodems are basically a sound card. They provide the actual modem functions in software. Said software is generally proprietary and Windows only. There were a few projects to implement an open softmodem driver for Linux, but none of them got very far. Some manufacturers released Linux drivers, but unfortunately US Robotics wasn't one of them.
Since you have a desktop PC with a PCI bus, you can buy a real (controller-based) modem and put it in. You'll probably be better off doing that than trying to get your softmodem working in Linux.