USB headsets & speakers are act as sound card by itself, i.e. your onboard audio adapter doesn't matters.

Look at getting started guide on official site - Support Knowledge Base | Plantronics . Headset is a completely separate sound device, so if you select it in Windows control panel as default device - all sounds will go to headset. If you want at same time also use other sound devices, you need for a software which allow to choose exact device for sound output, like many games or some media players (MPC-HC is a good start).