troydi, by 2.1, I assume you have a sub-woofer with your stereo speakers.
Cables should be colour coded to rear of PC unit and be marked with a small Icon as well. Is the buzzing coming from one of the stereo speakers or the base unit? Have you double checked you have them plugged into the correct holes?
One of the units will have controls on it, this will have the amplifier/transformer inside and maybe it is this causing the buzz.