For a year or so I used Poser on a laptop that had a 1.8 gig processor, 512 DDR ram, and 40 gig hard drive.  I didn't do very many complex scenes and when I did, or even sometimes when I was just trying to render a single figure with big texture maps, I had to do the following in order to do the render, and sometimes still have to depending on the scene I'm doing:

1. I set up my scene and then save it and close poser.

2. Then I go to my texture folders for the items that I have used and save a copy of the original textures to another part of my hard drive, so I didn't overwrite them. 

3. Then I go to my graphic program and resize all of the textures in the texture folder  that I'm using in that scene so the longest side is 1024 pixels.  I use bicubic resampling so that it doesn't get blurry.

Most of the time that works and allowed me to render.  Plus I have to hide lots and lots of things in the scene and sometimes render in bits and pieces and assemble in my graphic program.

However, if that doesn't do the job then in render settings I will lower the texture size from 1024 to 1000, and sometimes even to 900.

Other things that can help:

1.  Reduce the bucket size. Try 64, 32, 16, 8. A lower bucket size means a longer time rendering, but Poser isn't using up as much of it's virtual memory and it's often enough to get a render off.

2. Reduce raytrace bounces. 4 is usually what people use when working with reflections and metal, but you can try 3 or even 2.

3. Render the image without shadows. Then do a render with just shadows and overlay the shadow render on the no shadow one.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi