I think u can have ur config like this !!
Code:
Primary Master=HDD
Primary Slave=DVD-Rom Drive
Secondary Master=DVD Writer
Secondary Slave=CD-RW
Reason for this kind of setup.....
HDD in Primary Master is a must as its has OS in it.
The reason why I have kept the config like this is for the Bandwidth...
If you write to a DVD or CD using ur DVD-Writer or CD-Writer the data is going to come from either HDD or DVD-ROM drive. In case of CD-CD or DVD-DVD copy the source is again DVD-ROM Drive.
So there is more bandwidth for the source drive as well as the Destination writer. So no need to worry about the Data Underrun errors or slow recording due to lack of bandwidth between the devices !!