Dual CPU – WinNT4 vs Win2000

I have a dual P-III 450 (Gigabyte motherboard) and am having problems with the CPU utilization on the machine under Win2000.

I did a clean install of WinNT4-WS and the CPUs at idle only register 1-3% utilization.

I do a clean install of Win2000-Pro and the CPUs at idle float between 40-55%.

In both cases there is nothing but the OS installed. Task manager shows nothing running. My user first noted sluggish response when we upgraded the machine from NT to 2000. Same thing, with NT onthe machine he couldn’t tax the CPUs under normal circumstances. After upgrading to 2000, the system ran at 50%+ utilization before opening any applications. That’s when I did the clean installs of just the OSes.

Any ideas?
Thanks
Mike