Don't run P5 on a machine lower than 1 gig memory or processor speed. I haven't used mine since I pre-ordered it because I had an 800 MHz, 512MB Pentium III that just wouldn't run it without crashing. The program wouldn't even load some times. With a Pentium 4, 2.8 GHz, 1 gig memory it runs just fine so far, but I still prefer Poser 4 and Pro Pack since I've been using it since it came out. Poser 5 has a lot of new features and has to be relearned again, so I'm waiting until I have more time for that. If you create large files like I do (3-5 characters in one scene), stick with Poser 4. Poser 5 is scary to me too. It looks like you have to be a mathematician to understand it and I never was good at math. If Poser 4 does what you want and like, I would stick with that. Maybe one day when you want to switch to 5 (or 6), it will have all the bugs worked out.

Poser 2, 3, 4, 5, 6, 7, 8, 9, 10, Pro 2014, 11, 11 Pro