Google 'Everset Home Edition'. Download it and run a hardware scan. It will come up with a report of all the hardware you have in your computer. It should also give you a model type for your motherboard. When you have that type:
"the name of your motherboard" drivers
into google. Download and install the latest drivers for your motherboard. If the sound is integrated then the sound drivers will be included with the general motherboard drivers. Download the drivers to a location you can later find/navigate to.
Go to control panel > system. Select the hardware tab at the top, then hit the device manager button. Something in the device manager should have a yellow exclamation mark to it. It should be called, 'Sound Card' or 'Audio device' or something like that. Right click it, and select properties. Then select the driver tab in the pop up menu. Select 'update driver' and a wizard will pop up. The wizard will give you an option to 'select the location of the driver if you know where it is'. Select that, and then browse to the location where you downloaded the driver too. And voila, you have reinstalled the driver for your soundcard.
EDIT: Give your device manager time to populate. It can take up to 5 minutes for this to happen on some systems. And I actually mean 5 minutes.