Why Are Some DVDs Incompatible With My Player?by James Red
There are many reasons why your DVD player won't play certain DVDs. More often than not, the problem is due to the age of your player or a compatibility issue related to region or video format.
Region codes are software lockouts that assign DVDs and DVD players to specific geographic "regions." DVDs made for one region won't play in another because of region codes. Special all-region DVD players can play DVDs from every DVD region, and many DVD players can play a DVD from any region after performing a "hack" on the player.
Two dominant video standards are used today, NTSC and PAL, and they are not compatible with each other. A DVD sold in a country that uses the PAL video standard (such as England) will not play in a player designed with the NTSC format. Some DVD players are compatible with both video formats. Many times these players are also all-region.
DVDs are durable, but deep scratches and damages to the disc surface can affect playability. While some scratches and imperfections can be repaired using special scratch removers, others can cause permanent damage to the disc. In this case, the disc must be replaced.
Recordable and rewritable DVDs are commonplace now, but they weren't always widely used. Many early DVD players are not compatible with these DVD formats, and any DVD video made on a home computer with a DVD burner will not play in them. This problem is less prevalent than it was in the past, and almost all DVD players made today support all kind of recordable and rewritable DVDs.
Even if a player can read burned media, it can usually only read a certain kind of burned media. A video burned to a DVD must be burned in a specific way. A WMV or AVI movie file burned to a disc will usually not play in most players unless it is converted to another format first. Special programs exist that convert video files to the right format before they are burned so most players can play them.