I am running Poser 5 on a Pentium 4 1.5 ghtz machine with 526 megs ram with Windows XP. I have an Nvidia graphics card, but there are no Poser related issues. I have a grapphire tablet, no problems there either. As to whether to buy Poser 4 with Pro Pack or Poser 5, I'd carefully compare features. P5 has more bells and whistles, but is much more complicated with a higher learning curve and poor documentation. I've tried to do some things with the new strand based hair, but to be honest I perfer the old Daz hair props. The materials room in P5 is enough to drive me to drink, it was much easier to change texture maps in P4. P5 does have procedural textures and gels, atmospheres not available in P4. So if you want more simplicity go with P4 w/Pro Pack, but if you must have atmosphere, dynamic hair and cloth, and procedural textures get the new version.