Sounds like what you're looking for isn't a lightsource, but rather the "incandescence" parameter on the material shader of affected objects. It adds color disregarding the surface normal giving it that glow quality. Other softwares like Maya and Cinema 4D are doing it the same way, but have automated it in their renderer to look for a flag from a light source to trigger it. In XSI you do it manually.
Matt
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Matt Lind
Animator / Technical Director
SOFTIMAGE certified instructor:
SOFTIMAGE|3D
SOFTIMAGE|XSI
Matt.Lind(at)Mantom(dot)net
Date : Sat, 1 Dec 2007 01:17:09 +0100
To : XSI(at)Softimage.COM