Vista 64 audio recording restriction

Applian Technologies' "Replay Music" (and likely "WM Recorder") warn of a Vista restriction on audio recording from the sound card and advise the same fix: going to "Control Panel" -> "Sound" -> "Recording", right-clicking and choosing "Show Disabled Devices," and then selecting "Stereo Mix" as the default input device.

Well, when I "Show Disabled Devices," the only other choice I get besides "Microphone" is "Internal AUX Jack : 2-NVIDIA HDMI Audio : Not plugged in" (which I cannot set as the default input device even if it were the one advised). "Stereo Mix" isn't shown/available

What do I need to do in order to capture & record streaming audio with WM Recorder?

Many, many thanks.