S-video-in not working

I'm using a Vistek GeForce4 4600 on WinXP. I installed the drivers from the Cd so I could use the s-vid out. Great it works. Now I no longer have a Tv in my room and I want to use the svid in, but I can not get a display. I downloaded the latest forceware and wdm drivers and the latest version of MPC but to no avil. The GameCube is producing a display, but my computer won't do anything about it. Its pluged into a vivo cable and it's all pluged in right. I've restarted time after time with nothing. Any help will be helpful, thanks.