The Service Control Manager (SCM) is a specialised process that is started at system boot. It is responsible for the following:

• Maintaining the database of installed services.
• Starting services and driver services either upon system startup or upon demand.
• Enumerating installed services and driver services.
• Maintaining status information for running services and driver services.
• Transmitting control requests to running services.
• Locking and unlocking the service database.

Service applications are launched by the SCM and interact directly with it via a series of specialised Win32 API calls. Regular applications do not contain these hooks and hence cannot be launched nor controlled via the SCM directly.

Consequently, you may want to convert your application to a service with FireDaemon if you have a requirement for it to be run at system boot by the SCM or require a level of fault tolerance that is not achievable by logging onto your machine and running it by hand.

Many applications are designed to be run manually or automatically from the Windows Start Menu / Startup folder. Many are designed to be run across other Windows Operating System platforms such as Windows 98 or ME where the concept of a service is foreign. Consequently, applications of this nature need to be converted if they are to be run as a service.

You can find more out about Windows Services by consulting this Microsoft MSDN Library article.