The first thing to find if you are unsure is the make of the prebuilt system or simply the make and model board in a custom case. You first have to find out if you are using the onboard sound or have a sound card installed.
Sometimes a quick look in the device manager will show if an expansion card is installed. But you can also download a free tool for details on both hardwares and softwares too installed on the system there. That one is the System Info for Windows tool found at
http://www.gtopala.com/
There's no installer with this. Once saved to a folder you can however create a desktop shortcut and simply double click on that to see the main window appear. From there you usually go right to the support site for the board or even brand of sound card installed in order to download the latest updates.