Please help?

Make sure your audio properties are set to the correct output. If you have a second sound card, this is the most common problem. On older systems, the PCI sound card takes over as your primary source of sound output and input, therefore your onboard sound is useless. If neither of these solutions help, it might be a problem with yoru speakers and in that case you will want to check to make sure they are working properly. If this does not work, go into your BIOS(assuming you are using onboard audio) and make sure your audio device is enabled, however this is unlikly beucase it would probably cause problems with windows media player when trying to play any audio. Lastly, there is always the chance that the audio is simply malfunctioning and windows media player, nor the rest of your computer realizes it.