wait, didn't moses say "ye shall have no gods before me"?  no, but seriously, xpdev, "you are correct" = "the lighting of the room is very different from the lighting of the background".  since the sun is coming in the window of your room, the buildings in the background should all be showing their shadowed sides.

in order that the room lighting be the same as the background lighting, apply an hdr or jpeg (4X hsv value) panoramic background image to bill's envsphere, then use the envsphere as a light source.  as the daytime panoramic background has a zone for the sun, set the poser infinite light to the altitudinal/azimuthal position corresponding to the UV co-ordinates of the sun zone in the panoramic background. this method is explained here: http://www.hdrlabs.com/sibl/archive.html