7.x PE could be run as service but 8.x PE cannot ??
7.x as soon as it is installed it gets a Windows service associated with it. This is the *only* way to run server on Windows platform, so it is a limitation in some ways since only Administrator user will be able to install and create server instances.
8.x PE admin infrastructure does not support Windows services at the same level as 7.x. There is a documented way to create Windows service for particular domain using sc.exe utility. Refer to Restarting Automatically on the Microsoft Windows Platform
9.0 PE installer will offer an option to create Windows service for the default domain created by installer. Internally the installer still relies on sc.exe and it automatically call this executable to create a service. If users would want to create additional domains, then they still need to create associated service manually.