I'm not sure what you mean by a fresh copy, new system or not you'll need exactly what version of Poser you are running, and if your Service Packs are installed.

Alot of Poser speed is in the users experience, and what you're really looking to do.  With experience you'll learn many ways to tweak rendering speed, from within the Render Options window.  Off the top of my head you should dissable rendering of shadow, and dissplacement(Or turn dissplacement way down to like .001)  Otherwise there are plenty of threads around here on that.   Other than that you  ned to ask yourself how often it's really necessary to do 1 of two things A.) Render animations, or  B.) Render Huge Life-Size posters.  The slant to these answers is that Poser is'nt a Network Renderer yet, so really there is still time in the learning curve to perfect still life skills...like I do on my 700Mhz Celeron with 756MBs of RAM, all day...

For tweaking things on the RAM side of things see this thread I just wrote a moment ago:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2668451

Cheers!