Windows media player

I have a codec problem in wmp - I have cyberlink powerdvd installed and the checkup utility shows it is the preferred codec. I can play any other files other than mpeg-2. I can play any dvd’s through any standalone player except windows media player. I have tried unistalling and reinstalling but no success also tried rollback and reinstall of wmp still nothing. I suspect a program has removed a much needed part of my registry because a trial period of another program other than powerdvd6 has expired. Please can anyone help me.