>When we create an event log, there is a source associated to it. The one I created indicates it. In Windows 7, I see that in the Event Viewer we can have a section for Applications and Services Logs. How can I have my source to have an entry in there?

Do you mean that you want your log entries to appear in one of the existing sources such as 'Application'? If so it's just a question of setting the EventLog.Source property. e.g:

 Dim el As EventLog = New EventLog()
        el.Source = "Application"
        el.WriteEntry("Oops")