On all Windows setups, best practice is to set Windows Sound Properties so that Windows does NOT use the interface as its "default playback device". Set that to the on-board sound card so that Pro Tools can have total control of the interface. If you need to be able to route non-PT sound to the same speakers, the best solution is a monitor/source switcher(like Audient Nero or Presonus Monitor Station 2). The cheapest solution is a small mixer with 2 stereo inputs(Behringer, Alto, etc have them for around $60).
