To do this, you must download and install the Hangouts Plugin for Outlook on your Windows system. After the installation, you'll see a new icon that will allow you to schedule a new Hangout from either Outlook Mail or Outlook Calendar. Users can also join a Hangout once they have received the email by clicking on the external link to join a room.
Google says you can also use Chromebox as well and continue with your workflow: "If you're deploying Chromebox for meetings, now you don't have to stop using Microsoft Outlook® to schedule Hangout video calls."
[via Android Central]