Yes, now I it works (anyway I don't know what was the problem, cause I did initialize DXDraw).

Anyway the Draw call doesn't work. It needs a TRect instead of a TDirectDrawSurface. I changed the line to this :

DXDraw1.Surface.Draw(StarField[D].X, StarField[D].Y, StarField[D].r, StarGraphics[StarField[D].Size],false);

where r is a TRect.
was this necesary?