For a start yur chipset is ETEQ 82C6638AT/6629 AGP chipset, and as for your sound problem, you might be best to go to start|Settings|Control Panel and select the System icon by double clicking it. Then click the Device Manager Tab and see if any yellow marks appear beside the audio device. If there is, it means it is not correctly installed. What to do in that case is delete it by left click once to highlight it then click the Remove button below. After that, click the Refresh button and let windows find the aound card. If you have the correct drivers for it, use them when prompted by windows when it reinstalls the sound card by the above steps.
If there are no yellow marks next to the audio device listed, then it is correctly installed. The next thing to check is that you have the speakers plugged into the correct hole at the back. If you are not sure which it is, try each one until you get sound.
If none of the above suggestions work, try a different sound card and see if that works.