How to separate Onboard soundcard sound from USB Headphones

I would like to use my onboard soundcard (Realtek) to play music out of for my wife on the speakers, While I use my USB headphones to listen to and play a video game. I know it's possible as I've done it before, but I can't figure out what I did to get it to work. I thought before I would pick my speakers as Default audio device, start up music/movie then change my default device to Headphones and then start up game, all the while the music/movie would stay on speakers and anything I started up after changing headphones to default would play out of headphones. I'm running Windows 7 x64. I do a

Question by user391559 on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.