MANNAR

Hi I am new to Lego, recently found lego dacta 9751 boxes in our school science storeroom with no software or connecting cables - from the interface to the computer. I have downloaded the software from one of the earlier posts here Thank you but cannot use the interface I found a serial cable and tried to connect it to the computer and the interface but it does not work - the message on the computer is cannot find the control lab interface, please help Thanks