I have used this class to import Excel files since a while. The main code is like this:

        ' Import from Excel
        Public Function ImportFromExcel() As Boolean
            Dim lcConnection As String = ""

            lcConnection = "provider=Microsoft.Jet.OLEDB.4.0; " + _
             "data source='" + cSource + "'; Extended Properties=Excel 8.0;"

            ' Assign the source directory
            oConnection = New OleDbConnection(lcConnection)

            ' Select the data from Sheet1 of the workbook
            oDataAdapter = New OleDbDataAdapter("Select * From [" + cWorkbook + "$]", oConnection)

            Try
                oDataAdapter.Fill(oDataSet)
            Catch loError As Exception
                cError = loError.Message

                ' Try to extrapolate
                Select Case cError

                    Case "External table is not in the expected format."
                        cError = aMessage(1, nLanguage)

                    Case "'Schema$' is not a valid name.  Make sure that it does not include invalid characters or punctuation and that it is not too long."
                        cError = aMessage(2, nLanguage)

                End Select

                Return False
            End Try

            ' Record count
            nCount = oDataSet.Tables(0).Rows.Count

            Return True
        End Function

One Excel file I have to import contains a weird configuration as I cannot import it. I get:

"Cannot update. Database or object is read-only."

Is this because the person who sent me the Excel has applied some kind of security or protection in the file?