NEC ND-5500A will not read DVD's

I am trying to read a DVD in a ND-5500A DVD device. The unit will read CD’s, but will not display a DVD data disk. I have uninstalled the unit and allowed Windows XP Pro to re-recognize the device. This device is installed in a Dell C610 Laptop. The firmware is at 1.51 and I have run out of ideas. Windows update indicates that all of the drivers are up to date. Any suggestions would be appreciated.

Thanks in advance