Task Manager runs at 100% for CPU usage

Windows 2000 sp3. 30gb IBM7200rpm deskstar.
AMD 1800+ with 1gb 266mhz ddr
Gigabyte 7vax m/b
I have noticed recently that even when no applications are running, task manager says that cpu usage is 100%. It recognises the true availability of physical memory and the commit charge(k) changes but Cpu usage remains pegged on 100%. What’s happening?