Problem was encountered in Windows XP
Problem Background: Just installed a new OS (Windows XP) everything is working fine, except when you play a sound nothing is heard. I check the audio properties at control panel, it is properly installed. We suspect that it has a defective onboard audio chipset, so we replace a PCI sound card, still the same problem. What I did is reformat the harddrive and repeat the whole installation process, and there you go sound comes back.
Cause of the Problem: Upon studying the case, it was found out that end-user tests Windows Media player in Windows XP without the sound driver installed yet. Windows loads a default sound device which is not its current audio device. Even if you installed the sound driver afterward, it wont revert to the actual sound device.
Note: To avoid this kind of a problem make sure to load the driver of your audio device first, before running Windows Media player