If your 80-line UDMA hard drive cable is a straight feed one, the old drive must be jumpered as Master with Slave and the second one as Slave. If it is a Cable Select cable, both HDs must be set to Cable Select. The old (master) drive should be on the end connector and the new drive on the middle connector.
Your BIOS should then recognise both drives as well as your optical drives.
If the two drives balk at being connected to the same cable, mount your new drive as master or slave to your CDRW drive, and if you have a DVD reader mount it as slave to your old drive.