After saving his money for a couple of years, by son bought a new Xbox 360 250GB console yesterday which is our first experience with xbox. The guy in the shop also gave us a new HDMI cable (though it is a Sony PS3 one, though he told us they all work the same). Anyway, we connected it all up to our TV, did the setup, connected it to our wireless network and downloaded the updates. However, although the picture is great, there is no sound. So we tried the composite A/V cable that was in the box, and that gets sound, but the picture quality is rubbish.
I've tried googling for answers but I'm getting so confused. I'm not sure where the problem lies. is it our TV, (a Phillips LCD TV, about 5 years old) is it the cable, or is it the xbox itself. I've been reading that some people have had issues since the new software update. is there something else I can try before I take it back to the shop.
Thanks in advance.