Quote - Blacksmith 3D has an uninstaller program.  Poser Library Uninstaller

http://www.blacksmith3d.com/free_poser_stuff.htm

Instructions on how to use

http://www.blacksmith3d.com/pun_help.htm

Thank you Mystic-Nights.  Now that I finally 'get' external runtime libraries, I'm starting to think along the lines of creating an external runtime library for each download I use.  (My only problem is that I don't know if their is an upper limit on how many external runtime libraries Poser 6 can have).  If I can use that method, then backing out a download is as simple is removing the external runtime reference in Poser, and then backing up the runtime to a CD before deleting it.

I think I've come around to Gareee's idea that hard drive space it not really the issue.  My real issue is making sure one download's files do not interfere with or overlay  another downloads's files, or the original poser files.  Separate external runtimes for each download would seem to solve that problem. I could add external runtimes to Poser as I need each download, and that could allow me to catch problems with particular download before things got too muddled. 

Hmmm, come to think of it, this would also allow me to use PDT after all. I would do data entery on a download only when I finally allowed Poser to recognize its runtime.

Thanks again, Mystic Nights.

And my apologizes to everyone else if my thought processes seem especially slow, over long, and cumbersome.