I have a dual-core P4, and I still very occasionally see high utilization when doing relatively simple tasks. The culprit? The McAfee virus scan software provided by my school. I think when really big series of writes are done to the HD it spikes CPU utilization as it scans those files.
Also, you will eventually need your 12 core processor to do your virus scanning + MS DRM (en/de)cryption + (RI/MP)AA file scanner + firewall + work related to your pretty MS UI ripped from OS X.