Hmmm.... I would think the Sound Card will take over from the Onboard Automatically; so it sounds like a Driver problem, or a Speaker Problem.
Did you use Drivers which came with it, or is it second hand?
A Knight is sworn to Honour. His heart knows only Virtue. His blade defends the helpless. His might upholds the Weak. His word speaks only truth. His wrath undoes the Wicked.