the sound is integated into the motherboard. you can add a sound card if you have a pci slot free on the motherboard. you will need to disable the integrated sound in the bios, shut down the pc then install the new card. on restarting the pc windows new hardware found wizard will start and ask for the driver, this is on the cd that comes with the card.
download your motherboard manual first to find location of the integrated sound.
creative have a range of cards to suit all pockets.