Sub SaveAs_Mass()
    Dim sFolder As String, sFiles As String, sNonEx As String
    Dim lPos As Long
    sFolder = ThisWorkbook.Path
    sFolder = sFolder & IIf(Right(sFolder, 1) = Application.PathSeparator, "", Application.PathSeparator)
    Application.ScreenUpdating = 0
    Application.DisplayAlerts = 0
    sFiles = Dir(sFolder & "*.xls*")
    Do While sFiles <> ""
        If sFiles <> ThisWorkbook.Name Then
            lPos = InStrRev(sFiles, ".")
            sNonEx = Mid(sFiles, 1, lPos)
            Workbooks.Open sFolder & sFiles, False
            ActiveWorkbook.SaveAs sFolder & sNonEx & "xlsx", 51
            ActiveWorkbook.Close 0
        End If
        sFiles = Dir
    Loop
    Application.ScreenUpdating = 1
    Application.DisplayAlerts = 1
End Sub