I get horrible buzzing....

I just get a horrible buzzing when I use this software, the background buzz is just awful, and when I set the noise gate so that it cutsout the buzz, it cuts out half the quiet notes when I play! How do I connect up my guitar to the soundcard without this problem occurring? I don't get it when I connect it up to the amp, so it's not a problem there, and I think the cable I'm using to connect to the soundcard is fine, so what gives? Where does all this noise come from?