You can't render in a new window in Poser 6.  What I do is do my render and in the upper right corner of the rendered window there is a small arrow.  Click that and there is a save option in there.  I usually save in .png format which is backgroundless when opened in a graphic program that supports .png images.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi