Can't kill a process - gives "access denied" error despite I'm administrator and properties show I have permissions

In Windows 10, I have installed WPS Office (of Kingsoft). Then I tried to uninstall WPS Office but it says "wpspdf.exe" is running.

I restarted the PC but still the same error.

What I tried:

• I opened Task Manager and end process there (tried both "end task" and "end process tree") but still same problem.

• I run process explorer as administrator, but I can't kill process there too.

• In process explorer I right click the process, open the properties, and check all my permissions. I have all the permissions and all the advanced permissions. But still I can't end the task.

• I did run some CMD commands and PowerShell like these (I run all
  software by choosing "Run as administrator"):

  This on PowerShell (using the PID of the process)

  Stop-Process -ID 2137 -Force
  

  And these on CMD:

  taskkill /IM "wpspdf.exe" /F
  

Then I get the error "There's no running instance of the Task".

• I tried a software named "Process Hacker" but still same problem.
• I uninstalled the WPS Office using IOBit premium, and tried the solutions above, but still the same problem.

Still it shows that wpspdf.exe has status "running" on Process Explorer or Task Manager (on details tab).

And there are several wpspdf.exe processes.

What should I do to kill the wpspdf.exe processes?

Solution 1:

Boot from a rescue thumb drive and delete the file "wpspdf.exe"

You can use this trial version to make a boot disc.

Once it is deleted you should be able to uninstall the software.

Alternate solution is use the startup tab in task manager and find wpspdf.exe in the list and un tick it, reboot and see if you can uninstall the software now.