You might want to consider upgrading to XP Pro instead of Vista. It ought to be an inexpensive upgrade since it's being discontinued (it was a $20 difference when I bought a new computer a couple months ago). At least it sounds as if you'll be installing Vista on a fresh hard drive instead of trying to upgrade a system that already has XP. It's less trouble with a fresh install than an install over the existing OS.

My visual indexes of Poser content are at http://www.sharecg.com/pf/rgagnon