With Blender 2.48:
1 - A sphere at the center: the Sun.
2 - Two or more circular paths (the orbits), each path having a sphere parented as ‘follow path’ (the planets),
3 - How give the planets DIFFERENT SPEEDS as in the reality, i.e., close to the Sun = faster orbiting (revolution) speed (imagine Mercury), farther the Sun = slower orbiting speed (imagine the Earth) ??? A challenge? A dream?
4 - My problem lies with the settings of ‘pathlen’ and the length of the animation (render settings).
5 - Thanks for your future answers !