Looking at my Samsung PN58C590 TV, I believe you might be using the wrong audio inputs. My TV has an input jack labeled "PC/DVI Audio In". According to the manual, this is the jack you use along with the "PC In" jack, which I'm betting is the input your VGA cable is going to. You'll need a different type of cable for the "PC/DVI Audio in" jack, one with male 3.5 mm plugs on both ends, the kind that fits into the headphone jack on your laptop. It needs to be stereo, or TRS, which stands for Tip-Ring-Sleeve, describing the three separate parts of the metal plug. These are easy to come by. Any Radio Shack will have them. (See link.) This cable works for iPods, CD players, and most computers. Just to be clear, this is a single cable with one plug on each end, not red and white RCA plugs.
If you want to test my theory, set up as you described, using the red and white audio inputs. Play something on your laptop. Using your TV remote, switch through all the inputs you see listed in the on-screen input menu. I'm betting you will hear sound via one of these inputs, but you won't have video, because your laptop's video is going to one input, and the audio is going to another. Your TV can only use one input at a time. I hope this helps.