Why does PD generate noise?

Let me explain: I'm currently using the onboard soundcard (ASUS motherboard with a c-media audiocard). I don't experience any unwanted noise when I use Cool Edit Pro, Windows Media Player, etc. for wave playback. But the instant that I open PD...i get noise! (a buzz and a hum somewhere around 800 hz). I close PD, the noise goes away. I open PD, the noise comes back.

Is PD generating this buzz? or are the drivers? or is the c-media DSP?

If I buy a MOTU 828 (or some other interface) will that noise go away?

If I use ASIO drivers instead of the standard drivers, will that noise go away?

p.s.: I'm using Windows XP.