My HP"big one" has Windows 7, 64 bit, and 4GB
This one, a Asus netbook, has WinXP32bit, and 1GB, and runs PoserPro2010, slow, but doable.
Just stay away from mosquito net meshes. (or big textures)
Or from complicated material nodes.
But for a quick test, up to and including Posette? More then OK.

In between, a PB with Windows32bit, and 2GB
A DELL netbook, Windows 7 32bit and 1GB

Just keep everything clean, drivers up to date, and well defragged.
All, once a day.

1.Ccleaner, Cleaning and registry
2.Advanced System Care, all but defrag
3.Glary Utilities, One step
Configure them carefully, and enjoy.

Anti virus, Windows Security Essentials

And now Smart Defrag2 also from iobit, free and in beta, but seems to be working very well.

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!