Cannot delete an existing service using sc command: The specified service does not exist as an installed service
Solution 1:
View the properties of the service and you'll see a "Service Name" and "Display Name". The display name is the one you see in services.msc, you need to use the service name with the net command however. Sometimes they're very different for example "Extensible Authentication Protocol Service" is the display name and "EapHost" is the service name.
Solution 2:
sc delete "SERVICE NAME". Don't forget to put double quotes around the service name (if it has spaces in it). If left out it won't delete the service.