All is working well in my HP ZBook15 G5. But why is my 'System' Process taking about 1% CPU when idle? Sysinternals Procexp show that the top system kernel thread CPU consumer is one driver that is switching in and out of context a whole lot: about 2400 Context Switches per second! and is utilizing the CPU unreasonably. A Every Context Switch has the overhead of saving the interrupted thread context and restoring the interrupting thread context.
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This faulty driver is HPMoA407.sys. It is a USB HID Upper Filter Driver distributed by HP for driving the HP Wireless Link-5 dongle. The HP Link-5 dongle is communicating with wireless mouse and/or keyboard.
Sysinternals Procmon show that there is a huge amounts of registry sync checks per second (A few hundreds) to the following key: HKLM\Software\Primax\Mouse Suite 98\Production Utility
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"Primax Mouse Suite 98" to was distributed by Lenovo. It seems HP used this suite as their driver for their wireless mouse/keyboard. But they forgot to remove the reference in the code to the original location of the Primax software in registry, causing this problem. The problem is constant and unrelated to mouse movements or keyboard clicks.

The workaround is simple. I created the missing key in windows registry and WALLA!. the kernel CPU utilization went down to about 0.3%, kernel context switches went down to about 365 context switches per second. Problem solved.