I switched from W2K Pro to XP Pro and there was a neglible difference when looking at 20 or so WU's under XP--not more than a couple of minutes and that may be due to angle differences. The only problem I have encountered are occasional (5%?) crashes of Seti Spy when rebooting, but a manual restart of Seti Spy always works fine. Setting Seti Spy to run in W2K compliant mode and disabling visual themes helped with the crashes.