Well, copying the main folders over from my backup drive did indeed work - Poser 4 now IDs as ProPack on the splash screen, and it reads all the PNGs in the libraries (which I think was new in ProPack).  Don't really expect to use it as much as the newer types, but I want it on my computer available for testing when I'm asked to beta-test products.
Thanks for the responses.

I still wish I could find such an uninstall-to-reinstall program, though.  I have several incredibly useful utility programs I use that I installed long ago from magazine CD's, links on tech forums and such without thinking to archive the distribution files - if I can't find a way to port them over individually I'm really going to miss them; case in point - File Finder, a fast non-indexing hard drive search tool that I use daily.