If you have already installed the operating system and are currently receiving a "code 31" error on the WAN Miniport (Network Monitor) device, follow these steps:
  1. Open Device Manager.
  2. Right-click the WAN miniport (Network monitor) device, and then click Update Driver Software.
  3. Click Browse my computer for driver software.
  4. Click Let me pick from a list of device drivers on my computer.
  5. Clear the Show compatible hardware check box.
  6. In the column on the left side, select Microsoft, and in the column on the right side, select Microsoft KM-TEST Loopback Adapter.
  7. In the Update Driver Warning dialog box, click Yes to continue installing this driver.
  8. After the driver is installed, right-click the device, and then click Uninstall.
  9. After the device is uninstalled, right-click the computer name in Device Manager, and then click Scan for hardware changes.
  10. On the View menu, click Show hidden devices.

The WAN Miniport (Network monitor) device should now be started and no longer have a yellow exclamation mark next to it.