First - Check all the cables are corectly connected.
Especially the IDE drive as it is possible to put the cable in the wrong way up, Normally the cut out goes to the top of the drive.
Check you do not have any bent pins on the DVD drive, if so you may be able to straighten then with a pair of Nose pliars -- VERY CAREFULLY
Try replacing the IDE cable with another cable as the cable may be faulty.
Check the power supply to the IDE cable and that it is set to Slave not Master or Cable select.