I think this is unlikely but, is there any way of getting a 2.5 scene into 2.49?
Yeah, open the .blend using 2.49b and whatever gets loaded is what can be loaded. In particular, don’t expect any animation data to be transferred because 2.5 uses a new animation system called animato.
If you need the animations try exporting/importing as FBX.
I know some people that are doing that and (for them) it worked pretty well.
What do they use to import .fbx into 2.49 ?