During installation of the driver, you are asked to disconnect and reconnect the DAC. This is where the program seems to fail.When you reached that point, before disconnecting the DAC did you check to see if there was a "safely remove hardware" icon in the systray area (at the lower right of the screen), and if so, if an entry corresponding to the DAC appeared when you clicked on that icon? If there was, that entry should have been clicked before disconnecting the DAC.
Also, the instructions here refer to connecting the DAC when prompted during the installation process, not to disconnecting it and then reconnecting it. Sometimes driver software has to be installed before Windows "sees" the associated hardware. Try uninstalling the DAC in Device Manager, then shutting down the computer, rebooting with the DAC disconnected, then re-doing the driver installation with the DAC only being connected after the prompt to connect it appears.
Regards,
-- Al