i would think the cheapest option would be a tv card. i have an old one lying around which would do it, not sure if it will work with xp though, it was designed for cable in the us so was not easy to use really. But you can get new ones cheap
wat u want this graphics card to do..... geforce 4 are cheap but then not that good anymore. personnally i would get an ATI radeon there by far a su....supperia....... a better graphics card.