Audacity actually does that, it's just not very intuitive and easy to guess the right settings. I think GoldWave can also capture sound.

In Audacity all I saw was select the input device, microphone or MS sound mapper. Selected the sound mapper, hit record, and it recorded silence while I had some wav file repeating through the browser.

Is there another hidden menu somewhere to further define the capture?

Try Fraps broseph, it has multiple sound capture options. PM if you need anything

Are you trying to pipe audio into a recording program? If so you will need to do a few changes to audacity and windows to make this work. Firstly in Audacity, within the Preferences window, in the Devices section, change the Recording Device to "Stereo Mix". Then in Windows go to your control panel or right click on your speaker icon in your taskbar and go to properties or in control panel go to your Sound icon and click it. In the Sound window, click on the Recording tab and if you don't see it, in an empty space in that tab, right-click with your mouse and select Show Disabled Devices. The "Stereo Mix" device should now be visible if your sound card supports it. Right-click on that device and select Enable, then click OK to save the Sound settings change. That should get you rolling. This will enable your sound card to send sound data streams directly to your recording device (Audacity). Also, while still in Preferences in Audacity, change the Recording Channels to 2 (Stereo) in the Channels drop-down list, if available. Restart Audacity and its ready to use Stereo Mix.

Now lets say you don't have a Stereo Mix option for whatever reason. Hope is not lost. You can also use an audio repeater. Virtual Audio Cable to the rescue!

I highly recommend this program if you plan to record multiple audio streams at once. Lemme know if you need help setting it up. The principle is the same.

Cheers.

yeah he wants to capture audio directly from the output, which Fraps can capture that just using the program.