If simply turning a light on or touching a PC with your finger can trigger sound out the speakers, neither of those actions has anything to do with software.
could be a ground loop problem. make sure the speakers and the computer are on the same 110 circuit, and you could try one of these between the soundcard, and the speaker
http://www.radioshack.com/product/index.jsp?productId=2062214&cp=&sr=1&origkw=Ground+loop+isolator&kw=ground+loop+isolator&parentPage=search
