You've probably got two IDE channels. There should be two IDE connectors on your motherboard. One is primary, one is secondary.

Each IDE cable should have 3 connectors -- one end for the motherboard, and two connectors for peripherals.

Make sure that the existing hard disk is jumpered as master, and is on the primary channel. Jumper the new disk as slave and plug it into the other space on the primary channel. Make sure that you get pin 1 (the red wire) the right way round. The connectors are usually keyed.

Jumper the CD drive and the DVD drive as master and slave (doesn't particularly matter which) and plug them into the secondary channel.

Turn the PC on. You shouldn't need Partition Magic. Windows (I assume that this is your PC, not your Mac) should just do the right thing.