Windows won’t recognize DVD/CD drives

Windows XP has suddenly stopped recognizing my CD and DVD drives. BIOS recognizes them and correctly identifies the HP DVD burner and a CDROM, but My Computer doesn’t show them at all.

Control panel/hardware/device manager shows both with the exclamation point in the yellow circle, and properties gives the message:
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Windows successfully loaded the device driver for this hardware but cannot find the hardware device. (Code 41)
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I know the hardware interface on the motherboard is working, at least to some degree, because the BIOS recognizes the drives correctly. And, I can’t even reload any drivers, since the CD drives don’t work.

The troubleshooter doesn’t help, so I’m stuck. What could be wrong?