Well the laser could have simply become bad. But usually it is just one or the other (meaning CD or DVD). I would suggest checking the cables going into the drive and make sure they are properly seated and haven't come loose somehow.
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Have you tried device manager to see if the drivers are installed? -computer -system properties - device manager- double click your dvd drive, it should come up "this device is working properly.
Note to edward7897 and alias SiennaHughes, stop the spamming.