Interesting--different video cards as well? I've never experienced that effect. I just ran a performance trace on Poser 4 and did a couple of renders (Min=2% Max=100% Avg=38%). Sitting Idle, the % of CPU usage is around the average 30-40%, during a render, it maxed at about 90%. The 100% was only when I had a dialog box open waiting for input. This is on an old system, Athlon 1GHz 324MB RAM GeForce 2 MX. I have no idea why Poser sitting idle would strain a system enough to kick the fan into high gear. I'd say run a performance trace and make sure it's really Poser that's doing it and not some other application. Maybe the firewall or something else interacting with Poser is the real culprit. If it's Poser then It's a mystery. CPU maybe--Intel vs. AMD, hyperthreading, who knows?

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken