You mobo must have 2 IDE channels. I have always been told its preferred to keep similar speed devices on the same channel (IDE cable one to CDR and DVD, IDE cable 2 to Hardrive 1 and 2). Remember you will probably need a jumper on each hard drive to set one to master and one to slave (should be marked on the drive how to do this). The 2 partitions on drive one should be no consequence, except the new drive will be the 3rd drive letter (CD and DVD, will probably move up one).