I have the same problem. But I can't believe that there isn't any solution for this with VGA cards. Because producing an other resolution (i.e. producing black stripes left and right) has nothing to do with the type of connection to the monitor device.
I am angry about this because I bought a new external monitor for my laptop (sadly widescreen, because other devices are not available any more) and can't play most of my computer games any more without distortion because they don't deal with widescreen resolutions.
I hope for a solution...