You'll want to leave the Hard Drive as Primary Master or you'll have problems booting to the installed operating system.
As for the cd drives, any cd/dvd writers should be installed as a Secondary Master and the cd-roms as Slaves...either primary or secondary, though it would make sense to save the Primary Slave position open for an additional hard drive.
Drives are assigned their roles in the machine by the position the occupy on the IDE cable and the IDE channel they hold on the motherboard. The end cable position is Master...the center position is Slave. Whether they are Primary or Secondary depends on which IDE channel of the motherboard they are connected to...the Primary IDE channel connector is usually blue.