When you use the Processes tab in Task Manager, you notice that the sum of the CPU value for the System Idle Process, which is the unused CPU percentage, and the CPU Usage value from the status bar may exceed 100 percent?
This reporting problem, which occurs on Windows 2000, Windows XP, Windows Server 2003, and later, is caused by Task Managers inability to associate interrupts, and deferred procedure calls, with the processes that request them.
If you require accurate CPU performance information, use System Monitor:
1. Start / Run / Perfmon / OK.
2. Right-click in the System Monitor details pane and press Add Counters, or press the + button on the toolbar, or press CTRL+I on your keyboard.
3. Select %Processor Time, in the Select counters from list, and press Add.
4. Select %Idle Time and press Add.
5. Press Close.
6. Press the View Report button, or press CTRL+R.
Windows Server 2003: Dee Monitoring server performance topic in Windows Server 2003 Help and Support.
Windows XP: See Using Performance topic in Windows XP Help and Support.
Windows 2000: See Monitoring performance in Windows 2000 Help.