Using Composite In Feed as a Webcam...

Hey. I'm new to this site, and I guess i can start out here by posting a question that has been stumping me for the past month or so. Recently (ironically, about a month ago lol) i picked up a GeForce4 Ti2400 for my computer i was building, and it is running great. What I want to do, however, is use the video-in from the video card and run it as a webcam. I am running WinXP, and the feed is detected in MovieMaker 2. Its listed as a "video capture device." The problem is, when I try to select that feed as a webcam, the feed isn't detected. (Actually, the video feed isn't even listed as an option to begin with.) By the way, I am trying to run it through MSN 6 as a webcam. I have found NOTHING on Google and am lookin for a solution!
P.S. - I was not sure to post this under Hardware of Software, because it involves a bit of both.
thx in advance,
-Will (stumped )