Well, Poser 5 in Firefly renders is much more time and memory consuming than Poser 4 (from my experience) and it tends to work better if you don't do other things in the background (though I have and have been able to render)...I often do my production render before I go to bed and hope for the best when I get up in the morning. Poser 4 (for me, in Windows ME) renders happily while I do other things on my computer (and is beginning to look like a speed demon by comparison)...I wouldn't do too many memory consuming things, but normal use seems okay. I've not a clue about animation.