This answer was kindly given to me by Karmjit Singh from the Microsoft Silverlight Forunm
Private Sub Button1_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles Button1.Click
If IsolatedStorageSettings.ApplicationSettings.Contains("MyCheckSettings") Then
IsolatedStorageSettings.ApplicationSettings("MyCheckSettings") = CheckBox1.IsChecked
Else
IsolatedStorageSettings.ApplicationSettings.Add("MyCheckSettings", CheckBox1.IsChecked)
End If
End Sub
Private Sub Button2_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles Button2.Click
Dim x As Boolean?
IsolatedStorageSettings.ApplicationSettings.TryGetValue(Of Boolean?)("MyCheckSettings", x)
CheckBox2.IsChecked = x
End Sub