How to fix Windows Vista Media Center dvd decoder error?

I am running a Vista Desktop. There is o problem with the system at all but whenever I try playing any video from Media Center I get a dvd decoder error. Am using this system since past 6 months but the error started just a week ago.

Any idea what has gone wrong? From my end I haven’t made any changes, neither installed/uninstalled anything. Somebody please help.

As the error itself says, the problem with Decoder required to play DVDs. Re-installing the Decoder should fix the problem but before doing the same you can download the Media Center Decoder Utility from here and see what exactly is the problem.