Have reinstalled Vista and Realtek HD Adio drivers. From the realtek panel I can test the speakers and get sound from my 5 speakers. I can't however get any sound from any software WMP, youtube etc.
Unplug the cord and plug it into a random other port on the back of your computer. Your PC will be like "LOL NEW THING PLUGGED IN". It's probably that the port you're using is defective.