I´ve tried to play some of my GOG games on my portable computer, but there are a strange problem. First time i´ve tried age of wonders and everything went fine, then after some minutes, the screen size was reduced. I´ve fixed this problem changing resolution to 1280 (·720 i think) but on lower resolutions this problem continued, obviously at that moment never mind, but when i´ve tried Planescape torment i had the same problem.
My monitor have only 14 inches and it´s really crappy to see it on a small window (really it is not a window, the gameplay appears on a small rectangle at the center (1/4-1/3 size) and the rest of the screen remains on black). My monitor is an acer aspire (low gama) bought on 2006 and it runs on windows xp.
Thanks to all.

Is it a desktop or a laptop and what graphics card do you have? If its ATI or Nvidia you should beable to go into the control panel for either and set it to scale the image to fit the screen.