I brought a new 20G 7200rpm WD hard disk to add up to my present 10G 5400rpm old drive. Is it better to connect like this? Primary Master: 20G 7200rpm new HD; Primary Slave: none; Secondary Master: 10G 5400rpm HD; Secondary Slave: CD Drive. Does the 7200rpm HD need a cooling fan?n If so, which one should be cooled down, is it the PCB side or the metal side?