Question : Problem: my 8600gt hooking up to hdtv no sound little picture

so i just got two 8600gt's and i have them in SLI mode.  i want to connect it to my hdtv. they came with an s video cable that goes into the hdtv fine, and i see the picture. problem 1 is that the picture on the hdtv doesnt take up the whole screen and i cant find out how to change the resolution to make it. problem 2 is that there is no sound coming from the computer to the tv.  do i need an extra cable just to get sound? before i just connected the s video cable and i got sound no problem. thanks!

Answer : Problem: my 8600gt hooking up to hdtv no sound little picture

First problem, s-video won't look good on an HDTV(especially a 1080p hdtv). I would suggest using a DVI to HDMI cable(this will offer the best picture quality) and then you will also need a separate cable for audio as s-video and dvi do not transmit sound just video. You could also use a box like this one.
http://www.hdtvsupply.com/2to1hddvisww.html