redrover,
What type of air-filter does your HVAC system use? A better filter will help reduce the dust. For a simple solution, try using an electro-static filter. I believe the 3M makes them and they can be purchased at Home Depot. An even better, but much more expensive solution would be an electronic air filtration system. That's what we use (my son is very allergic to dust and dust-mites). Those systems can cost $500 or more. But even so, our house still gets dusty. As Cynthetiq said, Dust Happens!
