Have some trouble. (change default player)

[Antebellum8]

So I installed Nero today, which included Neromix. When i started to play my video files, it played on the Neromix player, and not Windows Media or Quicktime, and I do not want it to play on Neromix.
Now I have unistalled Neromix, Nero all together, and I have also installed limewire a couple of times, and now my files will not play on anything. Is there anyway I can change the standard player for my video files, or make it so that my avi, mpeg, mpg ect. files play on Windows media, and my mp4s play on Quicktime?