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
- Start -> Run -> regedit
- Goto HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video
- Select the subkey that represents the video card you are currently using.
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.
- Backup the 0000 and 1111 keys.
- Select the 0000 sub key and search for your HDMIs resolution. In my example its 1920×1080.
So search for the entry DALR6 DFP1920x1080x0x59
- Edit the key that matches your resolution and change everything to zeroes.
- Click Ok and then edit the corresponding key in the 0001 sub key. Change that one to all zeros as well.
- Go back to your desktop and change your monitor resolution and then change it back to 1920×1080
The underscan should be gone now! Can confirm that this works with Radeon HD mobile 4200 video cards.