How big is this green space? Is it around the whole screen, or just the top and left sides of the screen, and only a few pixels? If its what I described save your money on buying a cable, it's not going to fix that. My game does it, and others if not everyone's.
Top left and bottom sides of the screen and it's about 1 inch on the sides and 0.5 inches at the top and bottom.
Curious: Are you also using an HDMI cable and if so what's the specific model of your monitor you're using it with?
(I have no such issue and I'm not sure many others do too)
Model: LG Flatron M2250D 21 inches. Also, I checked and it doesn't have a socket for a DVI cable... Just the VGA and HDMI (which I'm using right now).