Both speaker systems sounded great plugged into the audio out of an old laptop, so I knew then that it isn't the speakers.
BUT....the speakers are powered and the headphones are not. (ground ?)

I have uninstalled\installed sound driver. Twice.

My wife does like to buy energy saving bulbs (I hate them) and I did turn off all lighting a couple of times when experimenting.

I'm the most puzzled by the difference between the rear port and the front port.
rear port- low frequency hum from subwoofer. Speakers sound clean.
front port- high pitch squealing in speakers-- subwoofer sounds ok. Zero low freq noise.:o

I am glad that until I solve this they are at least functional. Using the front port, the squeal is only audible when speaker volume it turned up about half way. I can max out the volume in windows and keep the speaker volume at almost the lowest level on the speakers, and that still gives me a pretty good amount of sound. I cannot stand to wear headphones for very long.

Next..will try to borrow an old sound card from someone.

I WILL post if\when I resolve this.
And......thank you for the help. MUCH appreciated.

I only have ATI overdrive to monitor temps. It never gets above 58C there.

The energy saver bulbs have a flourescent coil inside. I know...they don't have a light starter like your friend but since you brought up lighting I just wanted to mention I had even tried killing the lights just so I could rule them out.

Hell, I killed everything using juice on this circuit breaker at one point or another.:damn:

:D I will endeavor to persevere.