One quirk of Poser is in how it handles shadows. The usual shadowmap system seems to do a complete Load Objects before producing each shadowmap. Raytraced shadows are slower to render, but doesn't need the multiple Load Objects, so total time can be less. But Windows XP is using enough of that 512MB that you can easily get into using virtual RAM, swapping to and from the hard drive, and Poser 5 doesn't seem to do things in an efficient way when that happens. I tell myself I should upgrade this desktop, when I get the money.