Particles and Rendering 2.5

Hello all and sorry for my english.
I’ve just finished a project (modelled with 2.42) where I’ve used some particles that follow a curve guide path and for rendering I wanted to use the faster 2.5 instead of the older and slower 2.49.
Even if the 2.5 is really fast, it ruins entirely the “ray of particles” wich become bigger and moreover it is moved in another point of the scene without a reason.
Why I get this problem? There is a solution that is not model all again with 2.5?

Edit: also the 2.49 give me problems: it doesn’t move and scale the ray but it change the “type” of emitter wich distort the initial idea of the project.