The following error message is received when upgrading Plesk:
"Error 1920. Service 'DrWebCom' failed to start. Verify that you have sufficient privileges to start system services"
The reason of the problem is that "DrWebCom" service is missing for some reason.
Run cmd.exe and execute the following command to create the DrWebCom service:
sc create DrWebCom binpath= "C:\Program Files\SWsoft\Plesk\DrWeb\drwebcom.exe"
Then either click "Retry" to continue upgrade or start it again if you canceled it before.
Note: Services mmc snap-in should be closed during performing any operations with "sc" command.