Well, i was over to a friend to 'fix' his pc so that he would be able to see movies. He had already prepared the software (or so he said). Ineed he downloaded "Ace mega codec pack", which IMO is a piece of ... . Why? It has n codecs for the same job. I can't understand why it's that popular as it causes more problems then it solves. (Examples: the clasic explorer.exe crash with movie files & thumbnail view, this one can be solved with a regedit entry)

My personal favorites are and will be these:

• FFdshow
  
• AC3 filter (for some reason sound is better with this)
  
• Quicktime alternative
  
• Real alternative
  
• VLC player (mainly for ogm and mkv video files - i'm a big fan of Anime )
  

With these codecs/program i never had a problem playing a movie.

Of course there is another alternative called, MPlayer, i use it mainly on linux. It's a program that has the neccesary codecs delivered next to it.