What do you mean by "won't enable?"
Try deleteing the drives from device manager and allowing Windwos to reinstall them. You might want to follow the steps in the DMA problems FAQ, even though this isn't necessarily a DMA problem:
Also, you might want to try physically disconnecting the LG and seeing if that changes the status of the other drives.
What's your OS, waht's your motherboard/IDE controller chipset, what are all your drives, and how are they configured on the IDE controller?