Disabling services that are not essential for a computer that is limited in resources will help usability, here is an example of a similar situation:

The computers specifications:

Windows task manager:

The above computer was at 100% disk usage for extended periods of time:

What was eating up all of the disk i/o?

 NTOSKRNL

Actions taken to mitigate the problem:

• Uninstalled some of the HP apps that run on startup.
• Disabled Adobe fast start/tray on startup.
• Disabled the services: SuperFetch, Windows Indexing and Windows Search.
• Turned off indexing on the boot drive.
• Ran BleachBit to clean up all the temp files, cache, etc.
• Ran CLI utilities:
  • System File Checker: sfc /scannow
    https://support.microsoft.com/en-us/instantanswers/bd832f07-1420-0c14-d2a5-0a5a24ba40be/using-system-file-checker-in-windows-10
  • Deployment Image Servicing and Management (DISM): DISM /Online /Cleanup-Image /RestoreHealth
    https://www.howtogeek.com/222532/how-to-repair-corrupted-windows-system-files-with-the-sfc-and-dism-commands/

Plan B:

• Updating drivers, for the motherboard, video, etc.
• Disable Runtime Broker

Other Sources:

• https://www.drivereasy.com/knowledge/system-ntoskrnl-exe-high-memory-or-cpu-usage-in-windows-10/
• http://www.guidingtech.com/58662/fix-disk-usage-issue-windows-10/
• https://appuals.com/high-cpu-or-disk-usage-by-ntoskrnl-exe-on-windows-10