I have downloaded some videos that are in mp4 format and my windows media player wont play them, i dk how to play these files on my computer, the file i am trying to play reads, Type: NeroShowTime.Files.mp4
WMP is a directshow based player. It will play anything if you have the directshow filters installed for it and there are certainly filters for handling mp4's. For instance Haali's splitter and ffdshow. It shows "Type: NeroShowTime.Files.mp4" since it would be associated with ShowTime. mp4 is an open format, nothing specific to Nero, although they have implemented their own chapters and VOBSub's (within mp4 specs and supported now by other apps).