look at where your speakers are connected to
if they ate in a slot towards the bottom of the case and horizontal,chances are you have a soundcard.
if they are vertical and towards the top of the case,it may well be onboard.
aida32 personal etd will tell you what you have click here
install and click motherboard/motherboard and look for "intergrated devices" on the right or
click multimedia on the left and pci/pnp audio and it should say if you have a soundcard