Sort of seconding kodeen's suggestion, look for an option to keep aspect ratio. What GPU does it have, and do you have the latest drivers? If you're lucky, the little graphics control program that usually comes with the drivers will have an option along those lines.
My laptop only has crappy built in Intel graphics, but in the control centre I have three options for display scaling:
Scale full screen (stretch if necessary),
Maintain aspect ratio (fill as much of the screen as possible while keeping the shape correct, fill the remaining space with black) and
No scaling (show the picture in the middle of the screen at the actual resolution and then fill the rest with black).
So yeah, look out for options like that. The second one will probably be what you're after. That means if the game doesn't support 1024x600 you can pick 800x600 instead.