Use RowsAdded eveent to set the checkBoxCOlumns value to true
Code:
    Private Sub DataGridView1_RowsAdded(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewRowsAddedEventArgs) Handles DataGridView1.RowsAdded
        DataGridView1.Rows(e.RowIndex).Cells(DataGridView1.Columns("Insert").Index).Value = True
    End Sub
Also add this to initialization of checkboxColumn
Code:
dataGridViewCheckBoxColumn1.Name = "Insert"