OK, this might be more of a general hardware rather general pc question, but anyway

The DVD player my parents have in their living room used to work fine, playing DVDs, VCDs and Audio CDs. Gradually, it started reading only some DVDs and some of them it simply refused to read...

Now, it won't recognize any DVD and it just prints a message "Please insert a playable disk". It still reads Audio CDs and VCDs with no problem whatsoever.

Any clues?