Not unless someone wants to write a mod for it. There's currently nothing out that can do that, and I doubt it will ever be made.
Sure there is.
Hit win+r to open the run dialog, type %APPDATA% and hit return. Look for a folder called GOG, or create one if there isn't one already. Inside that create a folder called Silver, and inside that create a file called config.ini, and type into it
That'll give you fullscreen, but it will be rather horribly stretched on a widescreen display...