Thanks for the reply. I checked the game directory and all i can see is a dosbox.conf file :S. I have however got access to a 'graphic mode set up application'. Will this do the same job?
Ah. i've just read online that, 'apparently', vista no longer supports fullscreen dos games :S. any ideas on how to get past this, if it's true?
my laptop is a sony vaio vgn-nr32m/s supporting vista home premium by the way.
You don't have to worry about the Vista thing... that's referring to native DOS support under Vista, but you're running DOSBox, which is a DOS emulator. DOSBox definitely works under Vista and should allow fullscreen.
That dosbox.conf file is probably what you want. Sometimes individual games can have their own tailored .conf files, and I thought that this might have beeen the case for the GOG version of Stonekeep (I don't remember and actually don't have it installed anymore). If Stonekeep is the only game you are running under DOSBox, though, go ahead and just change the general dosbox.conf file to get it to work. Check the resolution options in the .conf file. You can also set it to default to fullscreen if you like. Look for the "fullresolution" option... my guess is that this is set to "original" meaning that it's trying to reset your laptop's resolution to match the game's original resolution. But if that's not a resolution that is supported by your laptop, it might lead to it running in a tiny box like it is for you. So instead you can manually set a resolution here. For details on editing .conf files, check out the DOSBox wiki: http://www.dosbox.com/wiki/Dosbox.conf
Again, if you can't get the options to work out, go ahead and paste the contents of the file here and we can take a look at them.
Also try running the graphics mode setup application (this is provided by GOG). It's basically a front-end to change some of the graphics settings in the .conf file. If it's set to "surface", try changing it to something else, because I've heard that "surface" does not allow hardware scaling which means your computer cannot stretch the image to fill your screen (and must instead reset the screen to the resolution of the game, which as I said above might not be possible on your computer depending on your graphics hardware).