Here's a list of mobo's based on the 975x chipset that will support 4 IDE drives:Click here for list
Be aware that the 975x chipset will only recognized 2 IDE drives. The other 2 IDE drives will be controlled by a seperate JMircon chip. Therefore when you go into the BIOS you will only see 2 IDE drives. The other 2 IDE drives will be recognized by the JMicron controller after the BIOS has loaded and before Windows begin to load.