P3 500 with 256 Mb RAM, Poser only ran out of memory once, whith PhotoShop open - as PS was set to take half the available memory I would guess that 128 Mb would be fine most of the time, but 256 (or so) is more better. I often run Poser and 3D Studio Max at the same time, make it simplier to check how your object mods are working.