Use smaller resolution, 640x480 is fine for most games. I have experimented a game with 1920 x 1080 , it looks nice, but just the fill rate makes it much slower. Use fixed resolutions which is faster than windowed and scaled.
However if you worry about HD graphics, make 1920 x 1080 based graphic and scale down in C2 layout, it would keep looking good even is zoomed in.