You can monitor how much memory any particular scene requires using the "Windows Task Manager" screen. Press the "Ctrl" and "Alt" and "Delete" buttons all at the same time - this brings up the Task Manager screen. Now click the "Performance" tab button. Down at the lower left you will see "Commit Charge" and "Total." Total is the amount of memory your system is using at that instant. "Total" goes WAY up during renders. Once the Total exceeds your RAM memory, your hard disc will start to work overtime to simulate addition "ram", and your system will slow down horrifically. Bottom line, when that hard disc light starts coming on a lot during renders, it's time to buy more RAM. But based on my limited experience, 1 gig is plenty for almost anything, except maybe for really, really crowded scenes, or scenes which use more than roughly 20,000 Poser hairs. Just monitor "Commit Charge Total" during renders to get a realistic idea of how much memory you really need for the type of scenes you do.