Trying to record from the sound card (Vista)

I'm trying to record streaming sound, so for that I read that I needed to enable and set "Stereo Mix" to default. It's weird though, because it doesn't work. Like I play some music, but the bars beside the Stereo Mix device stay the same. It's a new sound card, so drivers are nice and updated, etc. Mic works fine, speakers work fine, it's just this.