I've only rarely hooked my laptop up to a TV as a second display, but I've seen this before. Different results from different TVs, but in one case I connected to an HD TV (1920x1080), set the resolution correctly in Windows, and still some of the layout was "off screen". Which meant to me that the TV wasn't actually displaying 1080 vertical lines, but probably 900 to 1000, with the rest being overscan.
So, how do you "correct" this? I honestly don't know the answer, or where the problem really lies. To me, either the TV is not displaying everything it should or Windows is not sending the right information to the TV. Probably the first.
There are a couple of things would probably try in this situation. Changing what Windows thinks the resolution of the connected TV is. I would guess this probably wouldn't do what I wanted, as either the appropriate resolution isn't available (Windows doesn't allow you to put in a custom resolution) or the TV would actually change to the new resolution and there would still be overscan. Or change the size of the TD's main window using the Display Management tool on the Preferences tab. Using that tool, you can adjust the size of the main window and its position. I would probably create a new screen, and add to that screen a single cell that has nothing in it, and set the cell's border to be a different color. You could then use the Display Management tool to adjust the window size and position until the borders of the cell are visible on the TV. After you've got the appropriate size and position, put the real layout back up and if there still appears to be overscan, it means the layout is too large for the actual window size. Then you would need to adjust the layout to fit the window size. And do all of this with layout scaling disabled. Once you determine the window size/position, you can re-enable layout scaling if it makes the layout look better.
Of course I haven't done any of this, so use this as a suggestion at most.