You only need to change the librarypref.xml file in Poser 5.  For poser 6 if you go to "Edit" and "Preferences" you should find something about collapsing thumbnails under one of the tabs.  Pick "Never Collapse" and then save the changes.

"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