A disc error may be due to having the wrong type of DVD in the player, having a dirty disc in the player or the disc having scratches or cracks. When it comes to the type of disc, it must be compatible with the DVD player for it to work.
When this error occurs, pull the disc out of the player and look at the underside for smudges and fingerprints. If these are present, using a soft cloth to gently remove them generally solves the problem. Cracks and scratches generally require replacing the disc because they prevent it from working.