Open the case. Check the cables.
Then test each one separately as a master (disconnecting the other). If both can't be found as a master without any slave interfering, either both are broken (easy to check with another CD-drive) or that particular IDE-slot is broken. Try the devices as slave on the same slot as your hard disk is configured, and you'll know much more.
What you can do with them, shows that they still have power. But it doesn't say anything about the data connection with the motherboard. That can be broken everywhere (motherboard, cables, electronics in the drive).
Hope this helps.
I have both a Atapi CD-ROM and CD-RW on my computer. I am unsure as to why this occured, but the computer couldn't detect the CD drives. Simply, they were no longer listed in My Computer. I tried to readd them using Add Hardware, and looked under Device Manager. The status for it reads:
Windows successfully loaded the device driver for this hardware but cannot find the hardware device. (Code 41)
It would appear that XP can't find the drives at all, yet I can still eject the CD drives and place CD's in them, and the LED on the CD drives work. Nothing appears to be wrong with BIOS (although I could be wrong), there are no viruses/malware/adware that haven't already been removed, I disabled then reenabled the drivers in Device Manager, but to no avail. I don't want to uninstall and take a risk reinstalling in case XP can't find the drives at all! I'm out of ideas, any help would be greatly appreciated.