have an HP laptop that has never left my living room since i purchased it a year and half ago. I ran an output from the headphone port to the back of my receiver ( mini phone jack to an RCA plug). It plays great thru my stereo as long as my lap top is running on the battery and not the main power source. When I plug my laptop into the 120v power like I always do, the sound is greatly distorted. I have tried other outlets for the power. Is the problem my computer or the power source? Any help is greatly appreciated