Your second graphics card seems to be slower or lacking some capability, this is quite common for dual-headed setups. But don't despair, you have several options:

Generally, try various values for the "output=" option. That might fix your problem directly.

But to play on your 17" screen, you could set "fullfixed=true" and "fullresolution=1280x1024", then you get a nice fullscreen image. (again, play with "output=" settings for several variants)

When you have mastered that, look in the patches forum for nice addons to make scaled graphics look better 😉

Thanks for your answer.
Your tip with the "output=" option works great, i first tried overlay and ddraw but it didn't help (with overlay it was more bad than before, nothing visible at the 2nd screen)
but then i tried opengl and this works absolutely great (no stuttering and other probs), so thank you for this.

But i even tried to use the fullscreen on the primary screen so i set fullfixed=true and fullresolution=1280x1024,
this had the effect that the oldgame i tried had a smaller window with smaler but sharper pictures or grafic.
But in fullscreen mode the visible or game area stays as small as it was and the space between game area and screen border is just black.
Is there a way to scale this?

As I said, you must play with the output setting when using fullfixed. What you are seeing is output=surface.