Just to add to that, there are similar utilities which defrag the physical RAM, and I happen to have one running on my machine. It may be helping. I got it off the cover disk on one of the British computer magazines, back in March... [Pauses to check] FreeRAM XP Pro, and apparently freeware. I've had renders hang for a while, but the taskbar indicator was ticking away, and suddenly there was a fair chunk of extra RAM available to the render. I reckon it's worth a try. At worst, you get an idea of how much RAM is being used.