Why does FileSystemWatcher fire twice

why does the FileSystemWatcher fire twice? Is there an easy way to fix it? Surely if I update or edit the text file it should only fire once?

this link here http://weblogs.asp.net/ashben/archive/2003/10/14/31773.aspx says

1. Events being raised twice - An event will be raised twice if an event handler (AddHander FSW.Created, AddressOf FSW_Created) is explicitly specified. This is because, by default, the public events automatically call the respective protected methods (OnChanged, OnCreated, OnDeleted, OnRenamed). To correct this problem, simply remove the explicit event handler (AddHandler ...).

What does "remove the explicit event handler" mean?

Imports System.IO

Public Class Form2

    Private Sub FileSystemWatcher1_Changed(ByVal sender As System.Object, ByVal e As System.IO.FileSystemEventArgs) Handles FileSystemWatcher1.Changed

        'this fires twice
        MessageBox.Show("test")

    End Sub

    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        FileSystemWatcher1.Path = "C:\Users\c\Desktop\test\"
        FileSystemWatcher1.NotifyFilter = NotifyFilters.LastAccess Or NotifyFilters.LastWrite Or NotifyFilters.FileName Or NotifyFilters.DirectoryName Or NotifyFilters.CreationTime

        FileSystemWatcher1.IncludeSubdirectories = False
        FileSystemWatcher1.Filter = "text.txt"

    End Sub

End Class