After Windows 8 install, windows not filling up entire widescreen monitor? [duplicate]

This is a common problem with default settings of Catalyst Control Center. To fix:

• open Catalyst Control Center
• go to My Digital Flat-Panels
• choose Scaling Options
• slide the slider all the way to the right (so that it is a 0%)

Had the same issue after updating to Windows 8.1. My ASUS HDMI monitor suddenly had the black border and fuzzy fonts. My second monitor, connected by old school VGA, was working just fine. And like your description, installing the Catalyst Control Center didn't work (no executable, the driver was the AMD Radeon HD 7500 Series).

After much searching, it was clear I had to set the overscan (underscan) value to zero, but without access to the Catalyst Control Center, I had to go into the Registry. From AMD Catalyst 12.6 Released (+ 12.7 Beta), I changed the registry and rebooted and the problem was resolved:

I've seen that on one of my computers that's connect to a monitor that only has HDMI input. Set it right and it would revert after reboot or from hibernating. I found a fix somewhere by googling sometime back.

Go to the following key in the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\video{####....}\0000

Create a new DWORD:

"DigitalHDTVDefaultUnderscan" = dword 0x0000

Note: there might be several {####....} , should be the one with most of the ATI settings.