i have feeling you are talking about connecting your tv to the same card that has the aerial connction to it?

if so this is probably an input to the PC not an output so you need to connect your TV Svideo to the PC's graphics card Svideo OUTPUT. on the 8800 card in the XPS system i belive it is inbetween the two DVI (white sockets) or at least next to them. if your pc does not have this you will need some sort ot DVI to Svideo or composite(yellow plug) cable.

sound will be dealt with as stated above by your sound card and will probably just be a small green headphone socket.