Am running xp pro P4 2.8 with 1gig mem and have done up to 780frames at intense firefly production settings with no problems. However, when I was using my old P4 1.8 with 512m mem and high production settings - I did get virtual memory problems and had to allocate more blank disk area for mem then when done with render - reboot. Which is why I bought the 2.8 ;-) I'd check to make sure you have v-mem set high and enough harddisk to cover it as I note that around 300th frame - my harddisk is blinking away and I have nothing else running - not even screensaver.