NSV Live Capture which comes with NSVTools inside Windows XP is a pretty guaranteed bet.
Make sure to set "Capture Destination" to a Shoutcast Host. The API used by NSV Live Capture is old and is expecting a Frame Grabber type card (bt848/bt878, etc) with either a Built in audio driver (which the 878 does have) or it will use your physical sound card (keep in mind many newer capture cards also support this mode, so try it!!). Also, many PC Webcam's support frame grabber mode and very often come with a built in audio device for input (assigned to the mic on the camera itself) and their cheep.
It should work in Windows 7 as the API for Video Capture hasn't changed much in many years but no guarantees... But if you break it, you get to keep both pieces.