Help me kill my buzz

I have a mixing console with 6 mics, a 4-track recorder and a laptop computer plugged in.

Yesterday, the system developed a loud buzz. I tracked it down to the Laptop. When it is connected to the power supply the buzz is there, regardless of the mixer setting. It is present in the entire system. When I unplug it and run the computer on the battery, the buzz is gone.

All components are plugged in to the same house circuit, but not the same outlet.

Do I need a new power supply for the laptop, or is there something more sinister going on...

I plug everything into a power conditioner like an ART 4x4 (~30-40 bucks new).

This will ensure you don't have any ground loops and filter out a lot of mains noise like pops from shorts when lights go on and off.

Yeah, what the good Dr said....Sounds like a grounding issue.

Talk to your parents. That usually kills any buzz I have.

Temporary Fix-
It was a grounding problem. For 69 cents, I bought an adaptor to plug a 3-pronged (grounded) plug into a 2 prong outlet. This lifts the ground.
Plugged it in and the buzz is dead.

Will a power conditioner acomplish this? (without the adaptor)

Thanks for your help.