HDD's work best alone on the primary channel, and can be paired with another hard drive as the slave.
If you put an Optical drive on the same channel as a HDD, it has a tendency to slow down the transfer rate
of the hard drive to match the rate of the optical drive. Most hard drives now run as either ATA100 (WD)
or some (Maxtor) run at ATA133. Since most Opticals run at 66, you could be slowing down the ability
of the Hard Drive to move data by 33% to 50% under it's design capability.
Be better to set the HDD by itself, and pair the DVD & CD-RW together on secondary channel .
The DVD should be the Master with the CD-RW as the Slave. Some say the Burner should
be on the master, but my experience is that it works better as a slave from the DVD player.