[direwolf-pgh]

onboard sound can be disabled in the BIOS (at the system POST) or by the OS itself in Device Manager

to check installed driver in Device Manager:

right-click My Computer > Properties
select Hardware Tab > select Device Manager
click "+" to expand Sound

(if you disabled the onboard soundcard it will not be in the list - or you may right click and disable via OS)

if there is a yellow "? Unknown device" in the list - it may be your card.
You can verify that the correct driver was loaded in the Device Manager

Edit: Your onboard soundcard probably has an pre-installed software utility - go to Add/Remove Programs to uninstall.