I don't think you can use a wired connection.
You can use any Intel WiDi or Miracast compatible wireless card in your PC to allow other devices to project to it (a full list is available on the official Wi-Fi website). Most Intel wireless cards will work (they're about $30, although require Intel CPU), just plug it into your desktop motherboard and you're ready to project.
Note that if you want to project FROM your desktop (for example, to use the Surface as an extended display), you'll also need a graphics card that supports it. Intel (integrated in CPU) and recent Nvidia graphics cards support it. This is not required if you only want to project TO the desktop.