   320x240x8 interp. OR 640x480x8 normal
  Which of the two is faster(DirectDraw). How can i create a simple interpolation in DirectDraw? 
  Maybe you should abandon 1997 techniques (like directdraw) and focus on up-to-date techniques. DirectX 8.0 dumped directdraw, and that was released in 2000 !Just learn DirectX 9 and use the sprite interface, it''s faster (and even faster on newer cards), easier, supports alpha blending, you don''t have to clip partially off-screen sprites.Personally I wouldn''t play a 320x200 256 color game anymore. 