i put halos below a mesh above the mesh is a spotlight and shadow is created by the mesh. the halo is so inside the shadow but you can still see it. nor does the halo cast shadows itself when i remove the mesh above it.
i have selected shade for halo.
the key info tells me that shade makes halos able to cast and revice shadows etc…
Shade doesn’t make halos cast and recieve shadows, it only makes it dependant on lighting (I think it only reacts to buffer shadow, not raytraced shadow).
There was a tut for halos casting shadows on the old blender site, im not sure if there are mirrors of them.
To make halos emit light, duplicate the mesh and duplvert a lamp to the new mesh, you will need to lower the power of the lamp
hope this helps