Most mobos with IDE support have 2 IDE channels - Primary and Secondary.
Each channel can support two devices, assuming that there is a) sufficient space and mounting locations b) power connectors (you can buy a splitter to provide additional) and c) a 2-device IDE cable (i.e. 3 connectors - mobo, master, slave). again, you can buy these if required.
IDE suports both hard disks and CD / DVD drives. Best not to mix them on same channel if possible for performance.
HDs on Primary, CD etc. on Secondary.
SD