Windows 7, left alone for 5 mins and system pushes cpu to 20% until i press a key or move mouse

I have scanned with avast a few times for virus's but nothing has been found, however.. every time i leave my computer for about 5 minutes the process labelled 'system' which is the 'ntoskrnl.exe' bumps the CPU of the entire machine up to 20-24% which of course spins the fans up high..

The strangest bit, once I press a key or move mouse the machine recognises i am back and system drops off to next to nothing.. I have googled it but cannot see anything that matches this scenario so thought I would ask on here.

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After reading through a link (Troubleshoot High CPU usage by the "System" process) from a commenter who has since removed their comment i arrived at..

This link (ntoskrnl.exe!_misaligned_access eats a lot of CPU when idle) which I then found the item within system ramping up cpu is ntoskrnl.exe_misaligned_access+0x3f0

The guys reply in the above thread is to kill processes that end up there.. but I'm not sure if that is wise?

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So i turned off the scheduled idle task and this has not made any difference, i just went away to get a coffee, returned to the sound of heavy fan use and cpu up to 20%.. the culprit in task manager, "system"

Answer

So it seems, touch wood, that i have finally fixed the issue.

After not getting anywhere with trying to chase down the system process being kicked off when in idle, i decided to install the latest updates.. wooo bad idea..

Down came this incredibly annoying windows 10 reminder. It reminded me about its presence 24/7 with it's logo in my task bar.

After reading a lot of tech posts on how crazy windows is getting with harvesting your data (must be turning in a marketing company :) probably something a little more invading but hey.. that's the world of free stuff right?

Anyway, i stumbled upon this blog post:
https://www.hackread.com/microsoft-updates-spy-on-windows7-8-users/

Which bascially says, get rid of these updates:

    KB3075249    !important one
    KB3080149    !important one
    KB2923545

    KB2970228
    KB3035583
    KB2990214
    KB3021917
    KB3068708
    KB2592687
    KB2660075
    KB2506928
    KB2952664
    KB3050265

    KB2726535
    KB2994023
    KB3022345
    KB3022345
    KB2545698
    KB3065987

Find with
1 - run cmd

2 - start power shell
3 - run this command replacing with the rel. code:

get-hotfix -id KB3075249

For each one you find and decide don't want, uninstall with:
1 - run cmd (2nd instance to enable you to keep powershell running)
2 - run this command to remove:

wusa /uninstall /kb:2923545

And guess what.. after removing all the updates mentioned.. my laptops fans no longer go mental when i leave the room for 5 minutes! I wonder what the f**k windows was doing?