1. What is the DVD model?
2. I would first update the driver from the manufacture's website.
3. What type of DVD reading software do you have?
4. What were you recently doing before the this happened? Any type of software changes?
I put a new DVD reader in my computer but tried to use another type of DVD reading software and they werent compatable...but it seems like you have been using this before.
-AMD Phenon X2 555
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-Rosewill 500W PSU