no im not talking about the font and icon size
if you have black borders between the edges of your tv and your actual windows workspace then you have a scaling issue.
your picture looks like this right?
what is the make of your video card? there is an option for "scaling" somewhere in the video card properties that needs to be adjusted (in your case, scaling you need to be increased to make the image "stretch/fill" your entire tv) make sense?
found these instructions for ati/intel/nvidia video cards
ati
http://www.hack7mc.com/2010/05/ati-gpu-scaling-removing-the-black-bars.html
intel
http://communities.intel.com/thread/26843
nvidia
http://forums.nvidia.com/index.php?showtopic=221337
at the last step you might have to check "enable desktop resizing" and then click resize
that will place 4 arrows in the corners of your screen and allow you to drag them into a perfect position to fill/fit your tv