My spotlight is actually at 5000% but attenuation is set to inverse square. You would need a lower intensity if attenuation is set to constant (the default). It actually comes out a bit dark and I set Exposure at 2.0 in postFX (also saturation 0.01, contrast 0.005). My spot is pretty narrow (angle end 38.5 degrees) because it's only hitting one window. I might still change the spotlight size to 20% to be not quite as sharp, I don't know.

It's positioned at xTran 0, yTran 27.378, zTran -14.79. The window glass is basically at 0,0,0.

I do also have some emission on the glass.

I also decided to increase the density on the fog so I could get better light rays. That added a lot of render time.

I originally set this scene up to work in Firefly (a very long time ago). I don't know if there's a way to do it for real in Firefly, so I cheated and loaded the light with the same image as the glass, then set the glass to not cast shadows. That's why I had that setting wrong when I went to do it this way and I had forgotten all the details of what I had done. In case you're curious, it looked like this:

I feel like that was a pretty good result for 2006 me!