Well mentioning the overscan got me poking around in the Catalyst Software Suite, but there were no overscan settings to be found.
So I clicked check for updates and found one. It was dated 07-24-12 v12.6, which was much newer than mine. After updating to it I got a whole different interface and found the setting which resolved my problem as shown here. I had to move the slider from dead center all the way to the right.