I have two cd/dvd rw burners on my HP desktop computer. Neither one is being recognized. There is power to both-the doors open/close. When I look in the Control Panel Device Manager, both are still listed, but they both have a yellow circle with an explanation point in the center. I run Windows XP, One of the CD/DVD RW is a NEC ND 1300A. The other is a Sony DRU 840A. What would cause both of them to stop working? I checked the wires, seemed to be ok. One is the Master and one is the Slave. Need help. Can't load a CD that I need for a new scanner I just got.