Sorry, the above suggestion assumes that you had previously
successfully watched DVDs using another product. If such is not the
case, then it would help to know whether or not you have viewed DVDs on
this system. If yes, and you only used WMP for this, then you need to
determine which DVD (i.e. MPEG2) decoder your system uses and reinstall
that. If you previously used software other than WMP, then, as I
suggest above, reinstall that.