Not exactly a direct solution, but you could use a cheap TV card (like a Hauppauge WinTV) in your PC, and run S-Video to it. Then just fullscreen the TV software. Works really well as it gives you a little more control over the S-Video input.
I do this from my A4000D (towerized), through a SuperGen SX, into a Pinnacle AV/DV video capture board on my PC. Then a 2-Port KVM switch from my RTG card (Diamond VooDoo Banshee, Mediator 4000).
You should be able to find a WinTV card pretty cheaply on eBay.