Consider this Windows 8.1 machine (in-place upgrade from Windows 8) with differing reports on its CPU usage. The machine is idle, and has been for 3 days. There are no CPU intensive tasks running currently nor over the 3 day idle period.
Windows Task Manager is reporting CPU usage constantly at an incredibly high value (and increasing over time!) at around 75%.
Process Explorer from SysInternals reports that the CPU usage is much different at around 42%
How does Process Explorer report 42.14% usage, but its columns report Idle at 57%, with the sum of the other processes not even approaching 10%?
Which of these two values should I trust more, and why should it be trusted over the other measurement?
How can I actually determine which process is causing Task Manager to report its values?
These Proc Exp metrics were taken with Administrator privileges, and with option 'Show Details for All Processes'