Hi guys. I just posted this text in another thread, but is completely relevant to this thread, cause it is exactly aiming at performence: speed, memory usage and prevent crashes. Two things i did to prevent software crashes (On XP) and have faster renderings:

1- Start -> Run -> type "msconfig" -> go to "Startup" tab, and uncheck all things you absolutely know that you don't need to startup when your windows starts. In doubt, leave it there (although it can be re-checked if you lack a functionality in some other software). Then, restart and open your software directly (poser, daz, carrara, bryce...) and 50% of the crashes are resolved.

2- Get the DownRezer poser utility (small software available here at renderosity), and use it to be able to put more people and clothing in a scene without charging your RAM.

I'm a dork, animating dorks: www.TheDorkers.com