C / C++ / MFC

	// Create mutex, because there cannot be 2 instances of this application<br />
	HANDLE hMutex = CreateMutex(NULL, FALSE, "MyAppName"); <br />
<br />
	// Check if mutex is created succesfully<br />
	switch(GetLastError())<br />
	{<br />
	case ERROR_SUCCESS:<br />
		// Mutex created successfully. There is no instance running<br />
		break;<br />
		<br />
	case ERROR_ALREADY_EXISTS:<br />
		// Mutex already exists so there is a running instance of our app.<br />
		return FALSE;<br />
		<br />
	default:<br />
		// Failed to create mutex by unknown reason<br />
		return FALSE;<br />
	}

"Ideas are a dime a dozen. People who put them into action are priceless." - Unknown