Very strange to see a dip like that …

Computers, Grease, Dirt &Coffee
Works for Windows 7, Windows 8, Windows 8.1 and Windows 10.
To fix your display:
Write down the resolution and display frequency your currently running at
For an example on my machine there were 3 sub keys under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video . We’re looking for the key that contains sub keys named 0000,1111 and video. The sub key with the ton of entries is the folder you want to be working with.
In my example {DD0F636C-AA03-420D-B43A-B3EC8A0BCA11}
So search for the entry DALR6 DFP1920x1080x0x59
The underscan should be gone now! Can confirm that this works with Radeon HD mobile 4200 video cards.