You must know what sound card you have. Look on your receipt/invoice for
the computer - ask the people you bought the system from, open it up and
look, etc.
There are applications out there that can identify what hardware you have,
but I think they all depend on a properly installed system - as I think they
pull the information from the registry. Perhaps they do not - so I will
recommend you try two different ones:
Once you know what you have, what next? Go get the latest driver for your
hardware/OS from the manufacturer's web page. For example, let's say you
have an NVidia chipset video card or ATI video card, perhaps a Creative
Labs sound card or C-Media chipset sound card...
Remove the card from Device Manager. When you reboot the computer Windows
will find the hardware and try to install the software for it. Have the
installation CD that came with the card handy. Windows may ask you to
locate the driver.