For Windows 7, right-click an empty part of the desktop & choose "Screen resolution".
On the right of the resolution bar is a drop-down arrow.
Click that and you'll see a vertical slider.
Move slider up or down to see what resolutions the graphics card supports.
Even if the resolution you need is not available at the top end, Windows will automatically adjust or "stretch" the image to fill the screen, but the trade-off with that is less clarity & sharpness which you may or may not notice.