"XP tries to place Bryce on "low priority" when rendering" I don't think so. I'm just test-rendering a pic with Bryce 5.5 minimised in background. When I moved it there, the memory usage fell down to 20 MB, but CPU occupancy constantly goes everywhere from 88 percent to 99 percent regardless whether it's in the foreground or in the background. And now the memory usage is climbing and is at 102 MB (should be around 170MB for the scene). You can only see the tab on the taskbar, btw, but the priority is on Normal just like it's for Opera where I'm writing this. Have you set your memory usage to be optimized for programs?

-- erlik