On Windows you have the option to set an environment variable as a User variable or a System variable. A User variable takes precedence when the variable is set both as a User and System variable. Setting a System variable requires admin rights and will be available to anyone who logs into the system. User variables are only available to the user but are generally fine for desktop applications.
However, some applications either run as a service or have a component that runs as a service. In cases where the service requires a license (e.g.: Capital Manager), it is imperative that MGLS_LICENSE_FILE be set as a System variable so the service (running under the System user account) can obtain a license.
If you get errors when starting an application service, ensure that ALL required variables are set as System variables.