Thanks to you both for the input.  I am going to see how much I and move to a runtime directory that isn't within the "Program Files" subfolders - just to see if it works.

Fixer, I think I located your recommended Vista site with a forum "search" (?computerperformance?) -- I'm not ever going to complain about a useful infomation source.  My permissions for Poser seem to be in order.  I still think this may be a UAC issue.  I had never previously disabled UAC, which is to say that from my initial installation of Vista (32 bit Business version) I installed all my applications (Poser included) with UAC active, and, at least in the case of Poser, I was not running "As Administrator".  Running "As Administrator" and having UAC enabled is also a PITA, requiring two extra clicks and interupting everything else I'm doing just to open the application.  Now that I've decided to leave UAC disabled I may reconsider that option.  Nonetheless, I think that installing and running Poser with UAC enabled and not "As Administrator" made Vista force my library additions into this alternate directory.  That directory must have also been where Poser stored the "key" with the serial number registration.  Anyway, that's my take on it...

Lesbentley, I have actually mostly enjoyed Vista - though obviously from the above discussion it has it's quirks.  User Account Controls have certainly been the most controversial of the major changes and this may be an example why.  From everything I have read, for personal home use by a reasonably computer-literate and careful user, turning off UAC's seems like an acceptable option.

Thanks again for your comments.