For whatever it's worth:

I run Poser 7 on my Vista 64 machine with no problems whatsoever, I simply installed the program to my c drive in a folder named Poser 7.

   IOW,  C:/Poser 7

and NOT in either program files directories     (x86, and regular)

But I also, first and foremost before doing ANYTHING with Vista, discovered the best way to disable the infuriating "permissions" issue that pervades the wacky world of Vista in the name of security. Mind you, my  Vista box is not connected to the internet, (nor will it be), so security is less of a concern.  I'm sorry, that was months ago, and I don't recall exactly what that best way is, but it took some research and some trial and error, but I finally got it to the point where I was never hassled again by lack of "permission" to do whatever the heck I want to do on my own computer.