Word to the wise.  I recently bought my dream machine using dual NVidia 4500's in SLI mode and Windows XP 64bit.  I am unsure as to whether it is the driver or the 64bit O/S but Poser 7 does not like one or the other.  I too am getting the mysterious crash to the desk top.  This usually happens at the very end of the render.  I have noticed that renders with a large amount of reflective material is more likely to cause the crash than those without.  Either way it's a damn pain in the arse.  There is an old addage with Poser.  Save and save oftern.  It applies today.