Then you'll have to download a new sound driver and install it. If you have a PC made by a major manufacturer such as Dell, HP, Gateway, eMachines, etc., go to their website for your driver. If you have a self-built or custom built PC, go to the motherboard manufacturer's website for your driver. If you still have your motherboard driver CD, you can use it if you wish.
BTW, please do not create duplicate posts for the same problem.