If you're glitch free and it isn't broken, don' t fix it.  Vista and Windows 7 have 'User Account Controls' and this may (has with some people) cause problems when running Poser from within the Program Files folders.  Specially if you add and remove content from your Poser Runtimes, Windows XP, to my knowledge, doesn't have UAC.  Were I getting a new Windows 7 box I would install any flavor of Poser right off the root directory, C:Poser #.  I tried Vista and while I could run Poser 6 I had to re-start the program a number of times before it became stable enough to work with.  The program kept hanging, moving the camera or toons was impossible and I would have to force a shut down.

You can read through a few more threads if you like.  Others were faced with the same questions.  I think Poser Pro is pretty stable and Windows 7 seems very stable to me.  I loved and will ever miss Windows XP Pro.  But I never did like change ...

Best Wishes,
Rªnce