Diagnostic policy service not running - Solution

The error might appear once you diagnose your network because of not working internet.

Once you see this message you could try to run the service:

1. Press Windows + R to open run.
2. Enter into input 'services.msc'
3. Press Enter
4. Scroll down and find 'Diagnostic Policy Service'
5. Right click on it and click Start

Once it finished you might get Error 5: Access is denied.

To solve it do this:

1. Open start
2. Search for 'cmd'
3. Right click on it and click Open As Administrator
4. Enter this: net localgroup Administrators /add networkservice
5. Enter this: net localgroup Administrators /add localservice
6. Close cmd window
7. Do restart of your PC.

If you don't have antivirus I suggest to install it on your PC. Some good offers of ESET antivirus. 

Also possible reason because of not legal windows. Another good offers Here.

If this didn't work you might try to solve it with regedit.exe help. More info on Microsoft forums here.

P.S. Let me know in comments section below, if this method helped you. Thanks