A friend sent me an MPG4 file; is there any way to open such a file in Windows, with either Windows Media Player, Real Player, or Nero?  I guess this is a Mac file because none of these programs recognize that file extension.  Is there a way to convert the file so I can open it in Windows or perhaps make some kind of change to Windows Media Player so it can open the file?

   If you update any of those software, they should accept MPG4.  Here is a link to update Windows Media Player - http://www.microsoft.com/windows/windowsmedia/download/AllDownloads.aspx