Are you having Sound/video problems?
When you play the files do u get No sound or no video?

This is very easy to fix

Go to a website called    http://www.mpcstar.com/    then click Download Now
Once you download it. Install it. This will update all your codecs in all players you have on your pc/laptop. 
Then play any file in windows media player or Mpc star player. Every thing should work fine

OR

U can try a player called VLC player
http://www.videolan.org/vlc/