on the back of the drive there is a place that has three rows of two pins and there should be a jumper on one set of pins.(CS, Slave, Master) if the drive is now in a computer and alone on the IDe ribbon then the jumper should be set to master. if there is another drive on the same IDE cable then the drive needs to be set to slave or master depending on what the other optical drive is jumperd as. in short if there are two drives one needs to be set to master and the other to slave.