read all of it through before attemping just incase your problem lies within the second paragraph
easiest way is go to the sound icon, right click it, choose playback devices, right click on the device you want to remove and click disable, then open up your desktop and take the speaker out (thing that's plugged into motherboard) , then uninstall it from control panel and clean up as u like
if the reason your uninstalling it is to get something else to work as your audio, just do to playback devices (as mentions before) and set the new device that you want to use as default device