Never mind that in fact :) Just one sprite should be enough. But you probably need to overlay over particles on it, so the blend effect makes it glow. Check out the file below. Take a look at the image used for the sprite.
http://www.rosscrooks.pwp.blueyonder.co.uk/particle_glow.zip
:)
http://www.rosscrooks.pwp.blueyonder.co.uk/particle_glow.zip
:)