I ran Poser 5 sp1 on a 450ghz processor with 256 mb of memory on win98, later winme. It ran OK . I was used to Pov-ray taking days to render so an hour for a pic wasnt an issue.    When that machine was replaced I went to my current system of athlon 2400 and 512 mb of memory.

Lightwave runs fine , even rendering , and Vue is OK, though renders take a while, Carrara 5 is good. There are applications that run well on limited systems.

Poser 8 looks like something to avoid till service pack 1 is out. I didnt have problems with Poser 5 but I wasnt there for its release. I loaded Poser 5 and sp1 during the install.