olnorton: Have you tried changing the desktop scaling in your video card control panel?
i think what he suggested would work even though its a bit of a pain in the butt
also might want to try changing the desktop resolution if that scaling option doesnt work for you
i also have the same issue on windows 8, i can hand pick my resolution but the screen does not go full screen (ie stretch to fit) it only has black borders if it is anything less than my native desktop resolution.
oh well, i guess changing the desktop resolution is gonna have to be my only solution. i wanted the game set to 1280x720 but my desktop is 1366x768 :(
(funny thing is my intel hd card does support 1280x720 but i have to force it with another program and task manager out cause i cant set anything even semi custom on desktop... weird intel hd cards are, their support site says they dont do it but they obviously do when a program scans for available resolutions... so picky)
oh yea and i cant disable my scaling setting with my video card, at least none that i can see with just useing software display options that came with the drivers
edit:
haha just tried changing desktop resolution and it still didnt help the black border in game.... oh well ... ive had issues with other settings in other games that run strangely or like crap with windows 8 (like biggs widescreen mod for the infinity engine games running like garbage, only on windows 8) oh well guess i should be greatful it works at all... maybe windows 8 will catch up soon with compatibility *fingers crossed*