Service not executing task

I got the sample from here: click

And just changed this:

void CSampleService::ServiceWorkerThread(void) 
   { 
       // Periodically check if the service is stopping. 
       while (!m_fStopping) 
       { 
           // Perform main service function here... 
         MessageBoxW(NULL,L"TEST",L"TEST",NULL);
       } 
       // Signal the stopped event. 
       SetEvent(m_hStoppedEvent); 
   } 

So,when I run that service it should crash my pc with messageboxes,but I get NO messagebox!

I installed the service and started it from the services window.Under status it shows as "Started".

Why am I seeing NO msgbox?