You would only encounter a 2GB limit with a 32bit version of Win7; the limit is per process, not per thread. Firefly is a single process, even if it is using 24 threads (dual H/T hex-core Xeons).

Glen is already running 16GB, so the OS must be at least 64bit Win7 Home Premium. If running Win7 Pro (or Enterprise or Ultimate) then that computer -apparently dual channel- would probably max out at 32GB (four 8GB DIMMs). The limiting factor would be the motherboard's main chipset.

Poser, through P6, was 32bit and single-threaded. P7's Poser Pro derivative was 32bit with a 64bit Firefly. It could dice the render up into halves or quarters depending on your processor. After that, all of the Pro versions offered full 64bit (both the studio and the render engine), and rendering was distributed bucket-by-bucket as cores became available.

The limitation you were seeing is due to the single-thread Poser (4-6) or P7Pro (limited to four blocks, I think), not due to 64bit Win7. Another possibility is that you had a 32bit version of Poser installed; rendering would be limited to 2GB even if the machine is 64bit with lots of memory

I have seventeen machines running 64bit Win7Pro (or Ultimate); except for Eir & Kara, each machine has two H/T hex-core Xeons, and I can see all 24 threads pegged during renders. I have exceeded 64GB memory used while rendering. So Win7 can definitely use all of the processor cores and all of the RAM available to it.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5