Often, when one writes a game, one wants a specific resolution to make sure that the game works as expected. Zoomed out textures may not look as nice and the speed could be affected too (drawing 1280x1024 pixels instead of 640x480 is more than 4x higher and all video boards won't be as fast as required in this case). Under MS-Windows you can ask the system to change resolution (size & depth) with a call to ChangeDisplaySettings(). Search on msdn for more info, you will see that all the available modes can be listed with different Enum functions and you can make the change of resolution permanent on your users!