Games NO LONGER running in fullscreen

Hi,
I've been playing games on my laptop for a year and a half both from disc and downloaded software, however recently they have stopped running in proper full screen, they have black borders around all sides of the game. This started after I launched a game downloaded from gog.com which ran smaller than my screen, then everything else decided to follow suit. I'm fairly sure it's nothing to do with any specific games settings, and I can't find any joy by looking at resolution settings. It seems like this new program (which I have now uninstalled) has changed a setting somewhere that I can't find. Any help would be greatly appreciated, as it sucks playing games in a tiny little window surrounded by black screen.
Cheers

Try System Restore those a restore point before you installed the game from gog.com

Hope this helps.

John