Wondering if anybody can help me..

[HAL-9000]

Righty. My laptop is connected to my amp via the headphone socket on the laptop to the amps 'CD-In' socket. When my laptop is plugged into the power socket there is a constant and rather irritating crackling coming from my amp, whether the sound on my laptop is turned on or not. At the moment I can also hear a distinct clicking every second or so - very regular - sounds mechanical like a clock ticking. Other times there will be an audiable squeeking and sometimes the noise is quite loud.

The odd bit comes when I unplug the power to my laptop and run only off the battery. The sound is perfectly crisp - no crackling or hissing. No squeeking or ticking. The sound is fine - as if I were listening through headphones (but listening through my amp, obviously). When I use headphones I do not have the same problem and there is no problem when using the laptops own speaker. It is getting quite irritating now and I am beginning to worry about the health of my amp, as it seems like the power going to my laptop is directly affecting it. Do any of you know what is happening here, and could anyone possibly suggest a remedy that would allow me to have my laptop both plugged into the power and connected to my amp? Thanks in advance.