My Performa 6400/180 has white noise coming from the internal and external speakers. The noise also comes out of the front headphone jack. I can turn off the noise by turning the internal speaker down and by putting a speaker wire into the back speaker out port (but only without speakers attached to the wire). Turning the system volume down does not get rid of the noise. The noise turns into a slightly higher pitch when I click on a menu button. This noise used to occur only after long cumputer usage-6 hrs, but now it's there right after bootup. PLEASE HELP!