Strange Sound Problem with Mic

So I'm having this weird problem. I like to be able to use my speakers and headphones simultaneously so I use a Y connector to attach both. I'd never had a problem with doing this until 7. What is happening is when I have them both plugged in if I turn the volume up on the headset with the volume control along the cord is inversely lowers the volume on the external speakers. The only way I can hear out of the speakers is if I turn the volume down on the headset. This is a PITA. Any idea on what may be causing this?

Does the headsets have a volume control in them? - How are you controling the volume?
Are you plugged into the lineout jack? if so you might try using the speaker out jack instead

The headset has a volume control on the line. When I turn the volume up on the line the volume goes down on the speakers connected to the same Y splitter. I'm using the green speaker port. The sound card is the default one that came with the HP Pavilion that I have. The audio device is listed as "ATI High Definition Audio Device" on a Pegatron NARRA3 mobo.