Hello,
The main cause for dvd players to not be able to read the discs and give you error messages such as "bad disc", "disc not recognized", etc is due to the optical lens being dirty or the discs themselves are scratched or dirty. There are a few more things that can cause similar problems, but these are by far the most common.
There are two ways in which to clean the optical lens, either manually or by using a cleaning disc. Using a cleaning disc is much easier and faster. Cleaning one manually requires you to open and remove the cover and the lens can be difficult to get to.
The following links from my tips and tricks will give you more detailed information on how to use both methods of
cleaning the optical lens. You can also review an easy way to clean your cds and dvds as well at the following
link. I would also like to provide you with some additional information about
common mechanical problems with dvd players in case you need future information about problems.
I hope this information helps solve the issue you are having with your dvd player. If you need further assistance please feel free to ask and I wish you well.
If you would not mind, please rate my help. I would greatly appreciate it. Thank You