I think you might have to physically change the way you drives are connected. What I would try is setting up both your CD and DVD drives on one IDE port. It slows down the hard drives if they are connected on the same cable as a CD/DVD drive anyways, so it is better to keep them separate. Maybe by putting the DVD drive jumpered as master and the CD as slave, the bios will detect the DVD first.
There is the possibility that the bios is too old to detect the newer DVD drive, in which case you may want to check out the motherboard manufacturer's website and see if there is a bios upgrade available. Just be careful, as you can toast your computer doing this, so read the instructions first.
Hope this helps,