LCD TV + Computer resolution mismatch

How do I get my comp to fill the actual screen (outlined in red) instead of an arbitrary inset? I fixed it in the past by switching between DVI outs on my card, but this no longer works for some reason. TV is 1366x768 and forcing this resolution with Nvidia's tool doesn't change anything. There are no overscan adjustment options in the set without going into the service menu, which I'm not going to do. I feel it important to mention again that I've had it working perfectly in the past running DVI out > adapter > HDMI in on the TV. The picture was beautiful; no overscan and almost 1:1 (I was missing one or two columns on the right iirc). Nothing I'm trying is working. Google doesn't know; I appreciate any comments or ideas.

What's your GPU and what drivers? Not much we can do without some basic information here mate....